For use you have about 800mb on dori kernel on stock is about 780mb. Ram management on stock is very good no bugs at all. On cm 10.1 and 10.2 people report very good performance on cm 11 with good kernel phone is blazing fast. But gaming on cm 11 suck because of luck proper drivers by samsung. On stock every game works very good and i dont remember but on cm 10.1 and 10.2 games work good too.
XDA Developers was founded by developers, for developers. It is now a valuable resource for people who want to make the most of their mobile devices, from customizing the look and feel to adding new functionality. Are you a developer?