When comparing PlayMaker + Unity3D vs Modd.io, the Slant community recommends PlayMaker + Unity3D for most people. In the question“What are the best 2D game engines?” PlayMaker + Unity3D is ranked 77th while Modd.io is ranked 94th. The most important reason people chose PlayMaker + Unity3D is:
You'll need to put more time in learning Unity + Playmaker compared to something like GameSalad. But once get the hang of it and familiarize yourself with what it's possible to build with them, it's quite easy to use.
Specs
Ranked in these QuestionsQuestion Ranking
Pros
Pro Easy to use
You'll need to put more time in learning Unity + Playmaker compared to something like GameSalad. But once get the hang of it and familiarize yourself with what it's possible to build with them, it's quite easy to use.
Pro Provides access to a huge list of assets through Asset Store
For those developers who can't afford an artist, or aren't skilled enough to create their own art, Unity features an Asset Store full of a wide variety of free and paid assets that can be easily added to your game. The Asset Store has more than just music and art. It also has code and modules that can be added to your game such as unique lighting or GUI systems.
Pro Third party plugins support
A lot of third party plugins have support for Playmaker. Playmaker team also invest time to add support for a lot of third party plugins.

Pro Elegant state-based visual scripting
Instead of a single "if this then that" event list which can become very cluttered beyond the most basic behaviors, PlayMaker gives each object a list of states where only certain events are triggered, and performing an action also changes state.
This allows for a clean, simple visual representation which helps break complex logical structures into smaller pieces, making them easier to understand.

Pro Powerful
It basically can do same things as scripting in Unity.
Pro Its Fun, its easy to script
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Pro Runs well on low-end devices
The game client doesn't use much CPU nor bandwidth.
Pro Free
By far, this engine is completely free to use.
Pro No installation required - super easy to get started
Modd.io runs in browser, it provides IDE, map editor, and asset manager all in one platform, so you don't need to download or setup anything.
Pro Easy to use free Asset Library
You can easily change your game assets (images, sound, etc) with a single click using modd.io Asset Library
Pro Has multiplayer support baked in
This engine supports up to 64 concurrent players, and hosts servers for you as well
Pro Perfect for Impatient game developers
It literally takes 5 minutes from signup to publishing my game
Pro Easy to use
Modd.io is designed for new/intermediate developers who wants to get into game development. You should be comfortable using the engine after spending about 15 minutes in watching tutorial videos
Cons
Con Comparatively high learning curve
Although C#, JavaScript, and Boo have extensive documentation available online, it could still be difficult to wrap your head around the library and Unity's component based system.
Con Limited tutorials
There are not a lot videos with Playmaker tutorials. Official text tutorials are also quite limited. Even not every action has a description on an official wiki.
Con Performance could be better for 2D
Performance can be a real issue with 2D games. Unity 3D is actually a 3D game engine, and drags a lot of overhead with it.
For mobile, one could never achieve the performance of more specialized 2D engines with Unity3D.
Con The engine is evolving in a bad way
Over the last updates, many useful features have been removed, making it harder to create more complex games.
Con Not very secure
Modd.io comes with its own security issues. Many of them have been used to destroy eachother's games, which completely busts your progress on your game unless you have backed it up by exporting it's JSON.
Con Not Possible for stuff
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Con Annoying asset size limit
Each asset is limited to 800kb (except for audio being 3mb) which is okay for simple assets but unacceptable for creating spritesheets for animations or tilesheets for the map.
Con Very flat map
No matter how well game maps are made, all of them look just not beautiful.
Con No/limited camera manipulation
You cannot create a shake effect which is also urgently needed in complex game creation.
Con Certain variable datatypes are urgently needed but do not exist.
Such datatypes as arrays composed of numbers, strings, etc are needed to create complex games but just do not exist in this game engine.
Con Joke-y community
Most of the staff team in the community are constantly behaving like jokers. It just always feels like 80% of the staff team is not the right pick for such a community.
Con The homepage is not good
The homepage allows players to join your game, but the way it works is just not good. The "unpopular 0 player" games get less exposure than the popular games. The tier system also puts a star on your game card which also lures players to your game making them think this game has a special event or something, giving a disadvantage to the less popular games which are still so called "Tier 1".
Con Not very powerful
This engine is ready to use right away, but already starts dropping framerate at over 1000 units which are not very active.
Con Tier-based servers with certain lockdowns
Modd.io "tiers" all the games you create. The very basic tier, commonly called "Tier 1" is very limited and removes motivation to develop a game.
Con You'll have to learn a new programming language
This engine has it's own IDE with a drag and drop style programming language. It does take a good 2 hours to get familiar with the API..
Con No lower level API access
You cannot access lower-level APIs through this engine, such as the renderer.
Con No single player support
All games in modd.io must support multi-player game mode.
Con Limited customizability
Modd.io is designed to be good at making "specific" kind of multiplayer games. Its strength unleashes if you don't care too much about the specifics in UI. For example, if you wanted to make a casual death match game, it is extremely easy to make it using modd.io. However, if you want to create a puzzle game with a unique UI, it becomes very time consuming.
Con No 3D support
This engine is limited to 2D only.
