They have each about 25 questions of which most overlap anyways. Some have both tags, others only one. After looking through most of them I think that at least 60% of the questions can be asked for all Street Fighter 4 branches.
Furthermore there are new versions like Super Street Fighter IV Arcade Edition and Super Street Fighter Arcade Edition 2012, which should have their own tag. But even I do not bother with creating the according tags and ask them for super-street-fighter-4.
The game engine is the same in all of them. The new ones have some balances, a bunch of new moves and characters.