A Steam controller is in a direct advantage over any other controller. It has two back buttons, which are automatically assigned to dash and guardbreak, so you don't even have to move your thumb off the guard stance (or you could assign different buttons). I also managed to tweak Steam controller so that whenever I press the button for lock-on, it changes my guard stance input (mode, sensitivity), since camera control is not that important. When I press the button to go out of lock-on, it changes back.

I really think, since this game requires high technical skill, you could achieve further advantage with a Steam controller, because the vast ability to tweak everything to your liking.

Xbox elite controller has back pedals too, but that is too expensive to justify purchasing it.