When comparing Elm vs Godot, the Slant community recommends Elm for most people. In the question“What are the best game engines for web games?” Elm is ranked 1st while Godot is ranked 3rd. The most important reason people chose Elm is:
Lack of run-time exceptions makes it easy to produce large swathes of reliable front-end code without drowning in tests.
Specs
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Pros
Pro No run-time exceptions
Lack of run-time exceptions makes it easy to produce large swathes of reliable front-end code without drowning in tests.
Pro Inferred static typing
ML static typing is great because it's always there, you just choose how explicit you want to be and how much you want the compiler to do.
Pro Super easy refactoring with very helpful compiler errors
In no other language you can refactor so easy without any worries, since the compiler will guide you through. It is like TDD but than compiler-error driven.
Pro Designed around high-level front-end development
As Elm was designed as a front-end langauge, it has out of the box support for things like DOM-element creation, letting programmers focus on their application logic, rather than implementation details specific to the web.
Pro Great and simple way to learn Purely Functional Programming
You can try to apply some functional programming ideas in other languages that have an imperative basis, but you haven't seen the real power unless you tried it in the environment of purely functional programming. Elm is a simple language with great learning resources and easy graphical output, which makes it easy to explore the power of functional programming. Plus programming in Elm is very readable.
Pro Good tooling
All major editors have great support. With Atom for example, Elm plugins are available for linting, formatting, make/compiler support and Elmjutsu will simply overflow you with super useful functions, like navigate to referenced definition and show expression type.
Pro Batteries included
The Elm Architecture means you don't need to spend valuable time and effort choosing the right frameworks, state management libraries, or build tooling. It's all built in.
Pro Static module system
Elm uses easy to use modules.
Use:
import List
import List as L
import List exposing (..)
import List exposing ( map, foldl )
import Maybe exposing ( Maybe )
import Maybe exposing ( Maybe(..) )
import Maybe exposing ( Maybe(Just) )
Creation:
module MyModule exposing (foo, bar)
Pro Missing syntactic sugar
Easy to learn, most functions have only one way, not 5 alternatives where you must study where to best use what.
Pro Growing community
Pro Interactive Programming and Hot Swapping
Support for hot swapping and interactive programming is included.
Pro Easy to code review
The lack of side-effects and simple, consistent language semantics make it easy to quickly review incoming changes.
Pro Higher confidence in code correctness and quality
Pure functions, immutable data structures, amazing compiler, clean and homologous syntax used for HTML, logic, and optionally to replace CSS, elimination of entire classes of bugs so you don't even need most unit tests. These factors lead to better code, better programs, higher confidence, and ultimately, more satisfaction.
Pro Not quite Haskell semantics
Luckily you do not have to learn Haskell to be able to do any Elm. It is meant to be a language that compiles to Javascript, so for Javascript programmers (Front end) not for CS students who want to learn as many different algorithms as possible.
Pro Fully dedicated 2D engine, no hacks
Godot has a mature 2D engine with many features used by modern 2D games.
Pro Lightweight
The executable is portable and less than 40 MB in size.
Pro Under constant development
This engine barely released one year ago has more than 1000 forks on github and about 100 developers. Not only that just a bit of browsing trough issues you will quickly find out the dev community loves new esp free technology and does not shy away from completely rewriting parts of the engine. The audio engine is being completely rewritten to use threads and so forth.
Pro User friendly UI for all your team
Non-programmers (musicians, artists, etc) can join the development easily.
Pro Free and open source
Godot is licensed under MIT license. Anyone can grab the source from here, and compile the engine themselves.
Pro Editor and runtime are fully cross-platform
You can run Godot on all 3 major operating systems (Windows/Mac/Linux) and build your game to all available platforms from each without any platform-specific work needed. All platforms including Linux are supported first class.
Pro Can be deployed to multiple platforms
Deploy games to desktops (Windows/OS X/Linux), smartphones (iOS/Android/BlackBerry), and the web (HTML5 via Emscripten).
Pro The list of supported languages is growing
Officially, Godot supported languages for now will be GDScript, C#(Mono), VisualScript and C++.
Pro Drag & drop interface
Many parts of the editor allow you to drag & drop, which makes working with assets and scene trees a joy.
Pro Integrated animation editor
Every property can be animated.
Pro Built-in physics
Add physics to 2D and 3D scenes, through rigid and static bodies, characters, raycasts, vehicles and more.
Pro Unified game editor interface
All the game development work is done inside one program: the engine editor. The scripting is done in the same program. No need for Eclipse or other front-end editors.
Pro Instancing and node concept makes sense
The node and the instancing concept work very well and helps developers to structure content efficiently.
Pro Fun to use
An important aspect that can't be grasped without using the engine for a few days. The Interface is evolving nicely and making games is just fun.
Pro Internationalization of the editor
You can change the language shown in menus. Godot translations can be found here.
Pro Easy to learn scripting language
Godot has their own scripting language called GDScript. The scripting language is easy to learn with Python-like syntax, but it is not Python. It's very powerful, easy to learn, and it's free of unnecessary things because it was custom built for optimized integration with the Godot Engine.
It can be used to add custom behaviors to any object by extending it with scripting, using the built-in editor with syntax highlighting and code completion.
A built-in debugger with breakpoints and stepping can be used and graphs for possible bottlenecks can be checked.
Pro Really good community
The community is great and really cares about the engine. It is easy to get help and to be part of Godot's future.
Pro Creating editor tools is a breeze
Godot Engine is itself a Godot game. By adding the "tool" keyword to the top of a script, you can design extensions for the editor itself INSIDE the editor. Integrating these editor scripts into a bundled plugin for sharing is extremely easy to do.
Pro Friendly towards Version Control Systems
The engine is build not only to support version control but to really use it. Scene files for example which usually get compiled into some sort of unreadable data stay in a text format - that way you can actually see your changes in a version control system like Git.
Pro Doesn't need to be installed into the system
Godot is very portable, you can download the file from a website then put it on a USB and run it on your other computer without any troublesome errors.
Pro Easily expanded scripting system
With 3.0's addition of NativeScript and PluginScript via GDNative, developers can easily define bindings for new scripting languages. In addition to the primarily supported C++, GDScript, VisualScript, and C# languages, the community has contributed D, Nim, and Python as well with more on the way.
Pro Incredible documentation after 3.2.2 beta
The documentation used to be weak, but now we have nathen with his help the documentation is the strongest advantage.
Pro Scene Based editing
Godot gives you the ability to create scenes to make your life easier, with reusable objects and things you want to incorporate in your games. This makes the game making processvery streamlined and organized.
Pro Built-in documentation linked to the internal ScriptEditor
The editor has a fully searchable index of class API documentation for everything the engine offers (NOT just a web interface). You can easily open the documentation for any class by Ctrl-clicking the class's name in the in-engine text editor for scripts.
Pro Simple and readable codebase
The engine's source code is easy to read and understand with a self-documenting approach to code design. You don't have to wait months or years for other people to fix an engine bug that is important to your game. Often times, you can spend an hour or two of your own time to fix whatever problems you encounter yourself.
Pro Easy to get involved
No need to learn anything with node, you can build a game without typing a line of code + has visual scripting.
Pro Engine is yours
There is no royalty and the game you made + engine itself is yours.
Pro Can be installed on Steam
You can easily install Godot via the Steam store.
Pro Comprehensive tooling
In addition to the scene editor and the script editor (with debugger), the engine also provides a tile map editor, an animation editor (not just for rigs), a performance monitor, a network profiler, and an audio bus console.
Pro It has a visual scripting tool (Godot 3)
It has a great visual scripting tool. It's a great choice if you don't like to code. This was however removed in Godot 4, so you will need to use the (still supported) Godot 3 branch for visual scripting.
Cons
Con Lack of typeclasses
Elm doesn't have typeclasses which means some code needs to be duplicated. A fix in a function that needs typeclasses means all of the duplicates need to be fixed too.
Con limited js interop
only one way ports are available as a crude js FFI. This means you can only call functions both directions but will not get a result.
Con Harder to get buy-in from devs and mgmt
It's a total divergence from what most people are used to in the JS ecosystem. The change in syntax can be scary, the change in approaching problems can be scary. The fact that it's not backed by FANG can be scary. The fact that it's not v1.0 can be scary. The governance model and the deliberately slow release cadence can be scary. There are a couple harsh medium articles, hackernews/reddit posts out there made by people with an ax to grind that can be scary if you don't have a better picture of the Elm community, the tradeoffs that have been made, or the benefits to be had over other options. None of these are good reasons to write off further investigation of a great tech, but it happens.
Con Code Repetition
Because of the lack of genericness Elm needs a lot of code to be repeated. There are 130+ implementations of map in elms core libraries.
Con Features get removed without warning
Often features that are deemed to be misused by the community like infix operators get removed without much of a warning.
Con Community harsh if criticised
If one even dares to start a discussion about a feature on elms slack, discord, subreddit or github one will be aggressively shut down often argueing that one should use purescript instead
Con Poor Windows support
Few if any of Elm's core contributors are Windows users and breaking bugs are sometimes left for weeks or months.
Con Good for beginners not good for experts
Development in elm is quite nice until you need some more advanced features. These however are actively discontinued and removed because elm wants to establish a "single way of doing things" philosophy
Con Updates break existing code often
The last few updates of elm broke existing code in major ways.
Con Adds an additional layer of abstraction
Some users claim that Elm adds an additional layer of abstraction, meaning that it is one more hurdle between the brain and the product.
Con Functional programming itself has quite a steep learning curve
Functional programming can be quite difficult to get your head around. It takes time to unlearn object orientational habits.
Con No Genericness in the future
Currently there is no code genericness like typeclasses possible, it has been officially stated that this will never change.
Con Not database-friendly
It is lots of work to make a server or database your "one source of truth", as Elm makes you write endless JSON parse boilerplate to talk to the server.
Con No Syntactic Sugar
Often you need to write longer and less readable code because there are no alternatives that are more concise.
Con Primarily supports own language (GD Script)
Although C# is also supported by Godot, it is only supported by a separate version, and Mono must be downloaded separately. While GDScript is very accessible, and if you know Python you'll pick it up fast, having to learn a new language to fully make use of the platform can be a bit discouraging. And for those learning to code as well as learning Godot for the first time, many would rather learn a language they can 'take with them' when they explore other platforms in the future.
Con C++ Engine API not very friendly
The base C++ code from Godot is not documented, it's hard to set it up, to compile and hard to extend, it could use better programming standards.
Con Annoying minor bugs
Minor bugs can go unaddressed for some time, due to it being a free program.
Con GDScript is quite immature language
GDScript is copy of python and the real problem is, it is not python. Which means it cannot have all the power and new features that is available in Python or other programming language.
It does have some good features but it is not good enough for what you need if you want to deep dive into game development. You can just feel that by the godot team is solving that matter by supporting mono version. Because C# is popular in other game engine and it contains all the new features that is available from new programming language.
If i give you very simple example for why GDScript is immature, GDScript does not support asynchronous programming. Which is very efficient for performance of your game.
You may mention about multi-threading because asynchronous programming is one way of multi-threading. However If you try that in Godot, you cannot multi-threading where you want to implement asynchronous system. For example, Autoload (Fake singleton) where you want to manage data in real time. Autoload is not real singleton. It is not a separated thread that manage data. Therefore everything is synchronous in autoload. Even though you create new thread from Autoload script, your game will just stop and wait for your thread to finish its task...
Con Godot 3/4 split
The recent release of Godot 4 brings new features, but isn't yet fully documented, and performance may not be as optimized.
Con No console targets
Given that you can target both desktops and consoles with the same code base in other engines, the lack of support for consoles in Godot is pretty hard to get past if targeting desktops for a game. But asking for an open-source engine to target consoles is probably too much to ask. But it would be interesting to see some legacy consoles targeted even if current ones cannot be.
Con It's hard to learn
Con Difficult to optimize
Godot has an OOP architecture. Everything is an object internally and data is spread among many classes, thus it's difficult to optimize (i.e. not cache friendly, difficuly to vectorize or paralellize, etc).
Read about "Data Oriented Design" for more info about the problems and solutions.
Con Strange terminology at its base
Scenes can be made up of other scenes. That makes some sense. But even the smallest object (or prefab or asset) in a scene -- such as that spoon on the table or the marble on the floor -- is still called a scene... except when it's called a node. This is a bit odd for those coming from other engines. With all the great decisions behind the basic design of this engine, the choice of this term from all the potential other terms out there seems really out of place and only serves as a constant reminder that not everything about Godot is great.
Con No built-in way to import atlases
Godot does not have an easy and automatic way to import atlases created by other tools. However, there are plugins that can be used to import atlases from other engines.
Con 2DPhysics is weak compared to Box2d
Box2d has much more features.
Con NoAdmob or other AdNetwork support
Godot has no native support for implementing advertisements into your game.
Con Many buggy and half-finished features
Con Hard for a Unity user
Coming from a Unity background, Godot engine is hard.