What are the various feature differences between different as3 authoring tools like: FlashDevelop,FDT,Flash builder? ref link
FDT and Flash Builder are very similar, both are based on eclipse and both share features such as refactoring, profiling and debugging. However FDT (enterprise) has more features. Useful features are:
FDT Enterprise is pretty expensive though. Alternatively, there is the free FlashDevelop, built on .NET - so it is pretty much for Windows only.
Its features are more bare bone but still has some things one would expect like code assist and does include support for Haxe which FlashBuilder does not.
There is also IntelliJ Ultimate edition which has support for AS3 but have not tried it. The flash guru Joa Ebert swtiched to IntelliJ from FDT for enterprise development http://blog.joa-ebert.com/2010/03/06/compiling-actionscript-in-the-enterprise/