On topic, the SC series can be played better on the pad. It's a fact that's been proven at practically every major tournament. The fact that you can map any combination of buttons to it totally removes the factor of the user messing up moves that require multiple buttons to be pressed at the same time. Nobody is perfect, but with the controller, you only have a chance to mess up with the directional input. And like it was said in a previous post, SC isn't a game that requires much input from directionals. You also have the benefit of the control pad not making noises when you're doing an input, so you have a certain element of surprise that you can't achieve when using a joystick. The clicking sounds from a joystick are used by your opponent to tell if you're about to do something.
If you're like me though, you can use that to trick them at times. At my age, I tend to rely more on mind games than reaction times. So it helps.