Cocos2d-x and Cocos Creator vs GameSalad

25% of iPhone games are made using Cocos2d-x.

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.

Documentation includes a programming guide, API reference, video tutorials and massive reference test code project showing all functions and giving working code to the user.

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.

It supports Lua and Javascript with full feature 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.

Cocos2d-x forums are active.

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.

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).

Because it is based on Pyglet.

On top of supporting pretty much all existing platforms (except consoles), Cocos Creator (Cocos's IDE) allows you to write 1 code that runs on Android, iOS, Windows, MacOS and HTML5 (not Linux though).

Through the use of SDKBox you can easily integrate 3rd party SDKs and plugins for each version of Cocos2D (Lua, C++ or JavaScript), you just choose the SDKs to integrate and SDKBox will do the rest.

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 SDKBOX sdkbox::PluginVungle::init();.

It has a built-in Python interpreter that allows for easy debugging.

Cocos Creator (Cocos' IDE) comes with scene editing, UI editor, animations & particle editors and whatnot. It's also easy to use and pretty intuitive if you read the official documentation & tutorials. Way way better than the old CocoStudio.

Hundreds of video tutorials available.

The Windows version is now upto date with all the features of its Mac sibling.

Can create and publish games for iOS, Macintosh desktop and laptop computers, Android, Kindle, Amazon FireTV and FireTV Stick, Windows 8 and Tizen devices.

Gamepad support is available as of 0.13.3.

The GameSalad Viewer is a free app available for iOS, Android and Kindle. Once installed on your mobile devices, you can deploy and test your GameSalad games live on any mobile device running the Viewer that is on the same local network as your dev computer.

This even allows Windows users to test their games on iOS devices without a Mac device and without any complicated code signing or provisioning profiles.

And, you can even take your games with you -- once loaded onto your mobile device, a history option caches recent games on your device without any connection to the dev computer.

Since the user mainly uses menu options there is very little code needed to be keyed in. This makes the code very easy to read and understand.
Hence there are many help videos on youtube

Extensive community of seasoned professionals in all disciplines (graphics, game design, animation, physics, music, video production, marketing, etc.) producing tutorials, videos, publishing tips, free templates and who are willing to answer forum questions and help newcomers.

Allows you to create expressions on par with LUA (it's back end-language).

Allows you to import JSON data for custom collision shapes to use with Gamesalad's implementation of Box2d physics.

Software prepares your app so you can just send it to Apple. All my games are reviewed with no problems.

The drag and drop editor makes GameSalad very easy to use, no programming experience needed.

Very quick to learn and great for making games. Community is very open and helpful.