I think a lot depends on the skills of the team.
If the team is mostly comprised of Visual Designers, perhaps with a background with tools like Flash or Unity, then Cocos Creator gives you a powerful Visual Designer and its component entity model is awesome in that it allows the developers to make component scripts that the designers can easily attach to nodes to add behaviours.
If on the other hand you have a team of software engineers who are going to want to create a top down design for the game using MVC or some terminology like that then Cocos2d-x is probably what you want: Cocos2d-x is going to give you full access to all the source allowing you to develop custom nodes, and do OS level things. However, with the export option in Creator 1.6.2, you will probably want to keep Creator as part of your content pipeline as your designers can make scenes and other assets that can be directly imported by your code project.
The Cocos Creator editor is, as said above - closed source, but your project - the project it edits, is based on OSS libraries available on github with the caveat that the cocos2d-x used by Creator is not the standard version but has been refactored to support Creators component / entity model, and the cocos2d-js version used is likewise a ‘lite’ version that does not support all the features of the standalone cocos2d-js download (stencil masks etc).