For Smash that isn't an issue, the official controllers are what the game was designed for. I'm just really curious/concerned with regards to 2D arcade fighters, as those are designed for arcade cabinets and their sticks rather than any consoles' official gamepad, and pretty much any arcade stick I can find has a turbo function on it. I fail to see how a tournament could be run at all unless everyone happens to have super-basic sticks.
Let me rephrase.
Use of the turbo
functionality is prohibited by all means, controllers with turbo functionality not necessarily, but there's more to it.
Well...you know how there is a consequence for pausing? More buttons in the middle part of the controller heightens the chance of a mispress, because if you hit pause
or activate turbo you're forfeiting a stock/dq'd.
It just makes sense from a competitive standpoint to lower the possibility of such an error to a point where it is non-existent, and for all intents and purposes, the Hori controller doesn't do anything the Gamecube controller can't do in Smash, and even more, you gain the benefit of a wired connection (however much of a benefit you perceive that to be).