The GC controller is amazing for Smash but it's time to move on. All the tourney Smashers except for me are all "B" words! The classic controller pro is epic and will work just fine. The button placement is more like N64 game, and if you played with N64 controller like I did you put your big ol hand on the outer prong.
Even for single player online, the tablet will be just fine. I am amazed I still have some really good GC controllers left, but seriously it is time to let it go.