Q:How does pressing 2 buttons at the same time even take longer. The very nature of pressing them at the same time means it wouldn't. If anything it'd take longer to move your damn finger over to the c-stick instead of just keeping them on the buttons you're using the whole game.
My assumption is that people never use anything else but Smash attacks.
It’s mostly an issue of aerials. More advanced play uses repeated jump, aerial, fast falling, L cancel to attack really fast, and it’s easier to do that with the C-stick. That’s about it, really. Even though Smash 3DS doesn’t have L cancelling (like Brawl), the habit is so strong it’s weird not to have that resource.
Playing the demo I also found the lack of a Z button bothersome. It functions exactly like the C-stick, as a shortcut to a command you can input with two other buttons (Analog/A; Shield/A), so I shouldn’t have a reason to be upset, but I don’t know, it seems slower this way.