When comparing Unreal Engine 4 vs GameMaker: Studio, the Slant community recommends GameMaker: Studio for most people. In the question“What are the best 2D game engines?” GameMaker: Studio is ranked 6th while Unreal Engine 4 is ranked 17th. The most important reason people chose GameMaker: Studio is:
Game Maker Language (GML) is the primary scripting language that is interpreted similarly to Java's Just-In-Time compilation used in GameMaker. It is used to further enhance and control the design of a game through more conventional programming, as opposed to the drag and drop system.
Specs
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Pros
Pro A visual scripting system for non-coders enables quick prototyping
Blueprints are authoring tools designed for non programmers so designers and other team members can help tweak and prototype. UE4's Blueprint scripts resemble flowcharts where each box represents a function or value, with connections between them representing program flow. This provides a better at-a-glance indication of game logic than a simple list of events, and makes complex behaviors easier to accomplish and games a lot faster to prototype.
Pro Lots of resources to learn from
Epic provides multiple official video tutorials, lots of free example projects and content, an extensive wiki and regular streams showing how to use latest features.
Pro Powerful material/shader system
Allows a texture/material artist or VFX artist to create amazing effects from the ground up.

Pro Free development license, including source code
The engine, including full access to source code, is free to use; a 5% royalty is due only when you monetize your game or other interactive off-the-shelf product and your gross revenues from that product exceed $1,000,000 USD.
Pro Realistic graphics
Pro Developers have full control of the engine and source code
UE4 gives full access to the C++ source code allowing editing and upgrading anything in the system.
Pro Dynamic global illumination with voxel cone tracing decreases the computational power needed
Voxel cone tracing is a similar algorithm to ray tracing, but uses thick rays instead of pixel thin rays to be able vastly decrease the amount of computational power needed.
Pro Easy to use animation blueprints
Unreal Engine 4 is one of the best game engines. It is super easy. It dosent require any use of coding due to Animation Blueprints
Pro Spectacular lighting visuals
Pro Cross-platform editor and export
This engine exports for a big range of platforms including Linux. The editor can be run on Windows, MacOS, and Linux (Early Access).
Pro Active community
Forums have many active and friendly members that are quick to respond and help out. Even staff is very active on forums.
Pro AAA Ready
This is ready to make the next AAA game.
Pro Fast compilation for quick iteration
Recompiling an entire game to test a small change takes up a lot of time. UE4 quickly compiles in seconds instead of minutes improving iteration time by an order of magnitude.
Pro Quick release-cycle
New feature releases can be commonly expected about once a month.
Pro Professional feature set for all aspects of game development
Almost everything a game developer wants has a deep and sophisticated tool waiting for them in UE4. No external plugins are needed to make powerful materials, FX, terrain, cinematics, gameplay logic, AI, animation graphs, post process effects, lighting etc.
Pro Proven track record
Pro No coding experience needed
Pro Gives developers access to a more fine-grained controle over the logic through the Game Maker Language
Game Maker Language (GML) is the primary scripting language that is interpreted similarly to Java's Just-In-Time compilation used in GameMaker. It is used to further enhance and control the design of a game through more conventional programming, as opposed to the drag and drop system.
Pro Extremely easy to learn
GameMaker: Studio is incredibly easy to learn. It requires almost no programming knowledge which means that those without the technical experience, such as designers or artists, can create their projects without the help of a programmer.
Pro Easy to find resources/tutorials/assistance
GameMaker: Studio has a huge following, tons of people put up tutorial videos, and it's just generally easy to find help. It has a huge community.

Pro Easy cross-platform shader support
Write your own shaders in one shader language and have it automatically ported to all platforms. You can even choose a specific shader language to wield the full power of the target device.
Pro Assets can easily be found in the official marketplace
Yoyogames website has a marketplace which opens up an opportunity for people to sell or giveaway created assets and resources (sprites, scripts, sounds, extensions, full source codes, etc.) for use in GameMaker. This benefits people who needs quality assets for their games, and for creative people to provide these assets for extra income. The Marketplace has a rating system so it can eventually increase the quality and competitiveness of the assets submitted.
Pro It has an IDE used for loading all of the assets
It is very easy to manage all the resources you want to put in your game, the UI widgets for each assets (sprites, sounds, backgrounds, rooms, objects and shaders) are intuitive enough for when adding or even editing the properties of each your assets. The included editors are also good and easy to use (sprite/image editors, shader editor and room editor).
Pro Extremely stable
GameMaker: Studio has been around since 1999 and has been used and maintained during all this time. This makes it an extremely stable game engine.

Pro Cross-platform multiplayer support
There is the possibility of creating games that interact with different platforms and is not that hard.
Pro Built-in support for pixel-perfect collisions
Enabling pixel-perfect collisions on 2D sprites is so easy many will likely turn it on when maybe they might be better off without it. Regardless, it simplifies small and/or retro console-like game work. This is a feature fairly unique in this class of game engines.
Pro Cross-platform
GameMaker: Studio projects can be deployed to: HTML5, Linux, Windows, OS X, Windows Phone, Android, iOS and PS3/4/Vita.
Pro Easy to use
Game Maker Studios simple interface allows for rapid prototyping, and easy development.

Pro Supports 3D
There is also 3D support that doesn't interfere with the primary 2D focus.
Pro Easy to add native code to GMS
Good extension support. You can do anything with gms! You just need to know how to code natively in the respectively export (like Android).
Cons
Con Very high build size
A blank project will build in to a minimum of 200 MB.
Con Slow
Compared to other engines, UE4 seems to perform various actions considerably slower. Actions like starting the engine, opening the editor, opening a project, rebuilding shaders, updating references, calculating lightmaps, saving projects, etc take long enough to get irritating and end up wasting precious development time.
Con Extremely long build times
Making a full rebuild, including engine can take a good 30minutes. If you plan to use Unreal professionally, you better get some licenses for Incredibuild as well.
Con Hard engine for beginners
This engine not easy for beginners
Con Steep learning curve
Especially when compared to its primary competitor, Unity.
Con No drawcall batching, performance is very bad on mobile
There's no dynamic batching support to minimize drawcalls. There's InstancedStaticmesh concept in UE4, but it's 3d only, functionally limited and requires hardware support which rules out most mobile devices.
Con C++ - oriented development cycle: slow turn-around times
The Unreal Editor is the main place to do stuff (of course), so if someone wants to do a lot of C++ stuff, the compilation and linking turn-around times can be painful. Still they probably are quite fast in comparison to the provided featureset.. Still ,they are far from optimal.
Con Poor documentation
Most of the "documentation" for code is actually just automatically generated from the source. If you're interested in knowing how things are supposed to work, you must either go to their answers site or pay for UDN.
Often their examples won't even compile, since they were written for now outdated versions.
Con Royalty based
5% of profits will go to Unreal after $3000 earned in a quarter.
Con They spend more time adding features than fixing existing ones
Con C# not natively supported
UE4 does not support C# natively, but this can be achieved through MonoUE, although it requires using the MonoUE fork instead of UE itself.
Con Poor source control support
Merge tool is not working.
Con Poor quality assurance on their releases
After each release they almost immediately release a hotfix. And another one. And another one.
Con Unreal Engine crashes a lot if you don't have the required system requirements
Con Sparse Resources for C++
C++ happens to be the main suite for Unreal, yet the documentation is very, very sparse.
Con Extremely poorly designed
The code is a mess.
Everything is connected, a single Actor is 1500 bytes, because it contains a million things that Epic once needed in a game.
Inheritance for AActor: AActor > UObject > UObjectBaseUtility > UObjectBase
Con Difficult for Mac users
If you're installing it on Mac, you simply download Epic games launcher and watch it download nothing endlessly.
Con Tutorials do not go in-depth enough
The blueprint tutorial just teaches how to turn on a light when you press f.
Con Proprietary
Con Not available on Linux
Con No Terrain Editor included
Con Bad support
The epic games team only assists with billing and account issues, not bugs.
Con Terrible physics

Con Frequent crashes
Often the editor crashes interrupting your work.
Con Poor error messages
Con Rarely works
Con The scripting language used is quite limited
Language does not support actual objects, structs, real data types, functions, overloading, even argument naming. Developers generally have to code around the lack of these features in very tricky ways.
Con No GUI editor
The GUI must be hard-coded, leaving a lot of tricky calculations and jumping through hoops to accommodate different devices and displays; it's probably the least developed and hardest thing about GMS2 compared to comparable engines

Con Destructive DRM
In late 2012/early 2013, YoYo Games released a version of their new Studio IDE for cross-platform development that would import games and destroy all of the image type resources for some legitimate purchasers of the software by superimposing a pirate symbol on top of the image. This was due to a fault in their digital rights management software implementation which they use as a method of combating pirated copies of the software. Though the false positives bug is reported to be fixed, the DRM is still in place and may affect placeholder graphics, etc. YoYoGames publicly stated they would remove the DRM at a later point in time, but that other less-invasive DRM techniques would remain.
Con Exporting to some formats costs extra
You need to buy extra modules to be able to export to platforms like Android, iOS, HTML5 and others.
Con No built-in refactoring tools
There are no built-in refactoring tools. For example, you can rename a resource, but GM:S will not automatically change the mentions of it across the code to the new name. Furthermore, because all file formats are text-based, basic refactoring could be achieved by simply doing "find & replace in all files" -- which is a feature offered by pretty much every external code editor nowadays -- but no such feature here. Hitting Ctrl-F will pull up a rather odd Find/Replace box but selecting a word before hitting Ctrl-F will not autofill the Find field for you like it will in most tools. Even that you have to cut and paste yourself.
Con The cost to buy for development is outrageous
The cost for this tool is hindering for indie developers who have little money to work with.
Con Bad history of ignoring critical bugs
In the past, the developer failed to update the software for iOS and Android when game-breaking updates were made to those platforms.
Con Development has been and will be cosmetic
The change from 1.x to 2.x was cosmetic, the engine and language stayed the same. The roadmap for future development is also cosmetic and includes updating the sprite editor, adding an audio editor, and adding a "mini map" for the IDE.

Con Poor level editor
No marquee select, no layers, can be glitchy, no grouping, etc.
Con Can't embed videos in game
Doesn't support embedding videos in a game.
Con Expensive for what it offers
There are several options with more flexibility, better learning resources, and a lower price point.
Con Proprietary language forces expensive "lock in"
Because it uses GML, a very non-standard custom language, new users do not learn a transferrable language and become locked in.
Con Tends to crash or not compile games properly
Con Poor accessibility and integration
Documentation and resources largely focus on proprietary scripting language, which is necessary for achieving full potential of the software due to poor drag and drop integration.
Con No way to activate or use existing modules
Support entirely focused on new iteration depriving even basic functionality of this version with any purchase that hasn't already been activated. It is still possible, thought not intuitive, to download this version on the trail screen for GM S 2. But no purchased (wildly expensive) module can be added any longer.
Con Code editor not friendly to indented code
While the editor of course has features for intending code such as auto indent and smart tabs that can be turned on or off, these features work in unusual ways and, overall, the editor is not very adaptable to various typing styles. Also, Home always takes you to position 0 and never to the beginning of the text no matter how many times you hit it. Thus, if you hit Home and then Enter a new line, with auto indent on, it will always mess up the indentation on the line following the new line leaving you to fudge around to fix it manually. If you prefer tabs over spaces, forget it. Finally, if you leave the GameMaker app and try to click back into the code editor, the code editor will not fully get the focus sometimes leaving you with the ability to type but not tab. It usually takes two clicks to fully focus the code editor from outside the GM app.
Con This is very flat for games
They are not beautiful - for example, Undertale.
Con Owned by a gambling company, Playtech
As opposed to other engines, which are open source or owned by game companies, GameMaker is developed by YoYoGames, which is owned by Playtech, a gambling software company.
