Another example where a stick would help is performing chun-li's ex legs after a light kick. You would have to use piano hands to hit from low kick up to high kick and return to low kick. It is just too difficult on pad. I'm sure with a lot of practice, it would be do-able, but yeah...
But don't get me wrong, i have some friends who play SF on pad. My friend Phillip, who ran that family video tourney, only plays on controller. He'll be at that gamer gathering thing.
I've seen some amazing pad players for MvC2 as well.