Difference Between As2 And As3?

Also, many of the class libaries have been update or removed, such as the Color class, (which now can be used by implementing the ColorTransform class or assigning a uint). I intially found Action Script 3 quite hard to learn as I had only ever programmed in Action Script 2 before, but AS3 is vastly superior and worth learning

There are many differences. Speed being a nice one. In the Flash player, AVM2 (which runs as3 only) runs minimally 10X faster than AVM1 which is for AS1/2. It's cleaner too and the scope problems are gone. It takes some getting used to for sure - I think your best bet is to just pick something and do it in as3.