. Interface is identical

. Can be faster because it is 64 bits, but besides that it is the same engine.

. Characters, if exported using COLLADA, will import into Maya in the form of a set of Maya bones + mesh skinned to those bones. You can then work with this directly, add on whatever control rig you want, or use the bones as a starting point to re-rig the mesh to your specs. But conform clothes import as separate chars, JCMs as separate morphs, so you may have to set some things up manually. Dynamic hair and cloth dont transfer (IIRC) and nor do any shaders, though of course you have Maya for all that.

Also if pt. 3 is your main reason to buy ppro, then just keep in mind that you can do the exact same thing via the free version of D|Studio as well. You dont need to buy ppro just for this.