the SNES and Switch being the only two to share a relatively similar button layout.

And the Wii/U pro controllers. And Wii U tablet. And the DS and 3DS.

Sony also made their bottom button the default “confirm/execute” button and the side right button the “cancel/backout” button. It just feels more intuitive to me.

Here to note that this wasn't the way it was meant to be, on their controller, hence the common confusion you tend to get with a lot of games. I think it comes about as a result of them maybe trying to tread more of a line between the two, as, though we forget, there were more in the race than just nintendo, sega, and later, sony, back in the day, and nobody had really "settled" the layout. Sega, obviously, went for a layout that is basically opposite to nintendo. I don't know if it's purely a region locked thing, or if it's a game-by-game sort of thing (which seems like a stupid move but whatever), but the button layout in america, for playstation, has tended to conform more to nintendo's layout, than to sega's. I dunno why, maybe it has to do something with the popularity of certain consoles to certain regions, or something along those lines.

In any case, O is originally meant to be confirm, the X is meant to be cancel, which I think makes slightly more intuitive sense, pictorially. The O is the positive, the X is the negative. Obviously, over time, this sort of became swapped based on region, and actually, the PS5 is the one in which it's actually become universal that the O is the cancel button and X is the confirm button, for the japanese. Which is probably fucking infuriating, for them, I'd imagine.