I use arcade sticks for games with tap moves: F,F; B,F; DB,F; B,B
I use pads for games with circular moves: QCF, HCB, F,D,DF
I know most fighters these days have both. But they usually lean more in one direction than the other.
I also don't buy multi-plat fighters on X360 because then I'm forced to use a stick no matter what. Which is fine for tap games like DoA, but SF and stuff is >_<