That's where you'd be wrong. There are some that some people claim to be okay, but they all suck shit compared to a halfway decent stick. Yes, a stick will most times cost more than a pad, but you know what costs even more than that? Buying a pad and then deciding fuck it this isn't helping enough, I need a stick anyway, and then buying a stick on top of the pad anyway. Just skip ahead to the buying a stick part.
It bugs the living shit out of me that I spent money on a somewhat nice PS2 hori stick that I will possibly not use again since that console is now put away. The idea of spending money on a new stick for the PS3 isn't appealing. But I spent a couple hours with XIII tonight and the dual shock just isn't going to cut it with anything beyond the most casual fucking around. I got about 3 combos into mission mode when I had to face the fact that my thumb is never going to move fast enough to handle the kind of combos required. I'm going to have enough trouble with multiple fingers. So right there, ANY pad is out. Yeah, I've seen some people hold a pad in a really awkward way so that they can use their fingers on the face buttons, but fuck that. That is complete nonsense.
Just go for a stick.
edit: and DEFINITELY don't spend any fucking $70 on a pad. That is madness. If you are going to drop that kind of money, you should already be buying a stick.