The SNES controller has concave XY buttons (and convex AB buttons).

This confused me, but there seems to be a difference between US and JP/EU SNES devices. The buttons are only concave for US, and they are in shades of blue instead of different colors.

I do miss the Gamecube controller, and absolutely struggle on Playstation since it doesn't have brightly coloured buttons to help me learn (I use an Xbox360 controller on my PC).

Maybe this is reaching but my natural thumb position over the ABXY set of buttons does result in a different perceived texture based on what part of my thumb is resting on each button. So that might be enough since we typically don't stray far from the cluster.

Xbox controllers have large buttons, small buttons, joysticks, a D-pad, and two different triggers on the back.

The A/B/X/Y aren't distinguished between each other, but I suspect the four throttles for a B-17 aren't either.

There's an interesting series on youtube where a gamer has his non-gamer girlfriend play through a bunch of games on her own, and one of the common patterns is that she has no idea where the buttons are, has to constantly look at the controller, is always pressing the wrong ones. The only game that actually solved this for her was the Legend of Zelda, which has prompts that show all four buttons ABXY outlined on the screen, arranged visually like they are on the controller, and then highlights the one you need to press.

> The A/B/X/Y aren't distinguished between each other

Sure they are - their layout is distinct and doesn't alighn with any other buttons on the controller. It's very easy to distinguish which one you are hitting even though their shape and size are identical.

The Gamecube controller did it better, I think. Each button was a unique size, shape and colour.