Thanks to the increasing popularity of Babylon, it has a growing community of helpful developers. It's easy to find help on their [forum](http://www.html5gamedevs.com/forum/16-babylonjs/).
Ranked in these QuestionsQuestion Ranking
Pro Great script language support
Especially with Cocos2d-JS you can develop games cross web and native, and the native solution have great performance with JS Bindings, much better than hybrid solution.
Pro A proven engine for mobile development
25% of iPhone games are made using Cocos2d-x (A Cocos2d mobile variant.)
This means you will not be alone in development, and will have access to a large community. You'll know you are developing for an engine that works.
Pro Highly active community for questions and support
Cocos2d-x forums are active.
Pro Supports 3D models with skeleton animation
A new feature since Cocos2d-x v3.1 is support for 3D models (in your 2D game), not only this but support for skeleton animations is included too! This awesome feature allows for impressive characters in your game along with easier, more fluid and realistic animations.
Cocos2d-x is not only open source but also supported by Chukong Technologies of China and USA.
Regularly updated and adding support for the latest technologies. 2014 has already seen the release of Version 3, a new Cocos Studio development toolkit (optional) and support for new technologies like skeleton animation systems Spine and Adobe DragonBone.
Pro Greater performance than high level APIs
Cocos2d-x is C++ based engine and it has CPU advantages for most platforms because of that. It uses polygonal mesh methods for sprite rendering for using GPU advantages. (You also use quad methods for benefit CPU).
Pro Allows for easy debugging
It has a built-in Python interpreter that allows for easy debugging.
Pro Great video tutorials
Hundreds of video tutorials available.
Pro OpenGL hardware acceleration
Pro Easy integration of 3rd party plugins
For example, if you want to add a rating plugin, you use
sdkbox::PluginReview::init(); and if you want to add the Vundle Ad Network SDK, you use the one packaged in SDKBox
Pro No external dependencies
Because it is based on Pyglet.
Pro Small (but helpful) community
Thanks to the increasing popularity of Babylon, it has a growing community of helpful developers. It's easy to find help on their forum.
Pro A good amount of easy to understand resources to learn from
Babylon provides a playground where you can explore examples and play with the code.
The official documentation offers a wide variety of well-written tutorials on topics from beginner to advanced.
Additionally, there are many tutorials written by the community available that you can find by doing a google search.
Pro Great base shader material
Pro Actively developed
Babylon has great project health, with activity on Github daily for bug fixes and new features.
Con Poor documentation
Most existing documentation is out of date. API documentation sometimes exists, though is usually just a one-liner and more often than not is completely absent. New features and significant system rewrites often make it to a major release without a single line of documentation accompanying them. Cocos2d-x family is developed by Chinese mostly, so market outside of China is not their main priority. Some tools (like Cocos Studio) have China-specific services and markets.
Con Poor support and non-existent community
Up until 2013, this was one of the best engines around. However, since then it was bought by a Chinese company and began stagnating - it's virtually in a slow death. Most developers abandoned Cocos in favor of more modern solutions leaving the community weak and the forums with little or no traffic. Although the Cocos2d-x Forum seems to have a decent community going.
Con Cocos2d-html5 is way behind Cocos2d-x
While Cocos2d-html5 tries to mimic it's Cocos2d-x sister and has the same people working on it, it has lots of restrictions compared to Cocos2d-x: no Spine mesh support, no 3D models, bad text label quality, etc.
Con Inefficiency in making 3D games
Con Fragmentation; hard to find useful tutorials
Cocos2d family includes different projects: cocos2d-x, cocos2d-html5, cocos2d-objc, cocos2d-XNA. Most tutorials describe techniques specific to single project of the family, and cannot be applied to other projects.
Con Can seem very complex for a novice developer
There isn't much documentation or tutorials.
Con Modest functionality
Almost all free alternatives are more convenient, faster, and more functional.
Con Young project
Babylon is quite young compared to many of it's competitors (released in 2013). The community is still somewhat small, however growing quickly.