I'm a new Flash games developer, i just created my first game in Flash using FlashPunk, it was great, now i'm supposed to create a single player vs cpu soccer game, exactly like this one : Kung Foot.
As i said, i find FlashPunk a good Framework, but i'm opting for better performance and heavy graphics, i'm actually think about either Citrus or Flixil.
They both use Box2D for collisions, but i've heard that Citrus would be the right choice if it was a platform game.
I don't know if there are any other well documented Frameworks out there, what do you think !
Citrus isn't really an engine as much as it is a collection of other tools to make development easier. It takes a rendering engine (like starling or away3D) and a phyics engine (like nape or box2d) and bundles them together for you, providing some functionality to make the process of using them easier. (Like the ability to add a virtual joystick to the screen in one line of code. However, you could do all of these things on your own and be just as successful.
If you plan on using Citrus, be very careful. It's great for getting stuff up and running quickly, but the documentation can be very iffy sometimes. For example SimpleCitrusSolver is used in a lot of their tutorial documentation, but it is broken in newer versions. I recommend reading about the logic behind every library function you use from citrus, instead of letting it be a magic library that does nape and starling for you.
As far as what framework is the best, it's really a personal choice. They all will let you accomplish the things you want to do, just go with what feels the most comfortable.