Extras' are good at everything snaps,spins,knife edge,rolling,etc.
Edges' are real good at freestyle and some stuff ,but snaps,and rolls are not two of them.

Yes there are some planes that do things better here and there but a Extra is the all around plane.Maybe not the best at any certain thing but all around the best.

I own a Edge and it is a Freestyle bad boy and it will do things that I have not been able to get my Extra to do.
My Extra will do everything good but not great.

Hope this helps