This is coming from someone who uses the Wii U Pro Controller (they ran out of GameCube Adapters when I purchased the game on launch day, so I decided to buy a Pro Controller because it was the next best thing. Believe it or not, I now actually prefer the PC over the GC controller).
Anyways, I set the C-Stick to "Attack" which allows me to use tilts in place of smash attacks. I personally like this a lot as it gives me a very easy and consistent way to do forward tilts (I tend to screw them up doing them with
+
). Also, the Smash Attacks of my two mains, Lucas and Shulk, are very situational so, in my case, it's basically giving me an easier and more consistent time accessing three, better moves for them. The C-Stick for the PC is also directly above the ABXY buttons while the GC controller has it a bit below. This means I can use the C-Stick for tilts, but not have to remove it from the same general area as the other buttons, unlike the GC controller.