Which button on a controller is used as the universal confirm button for (nearly) all games on a console and its underlying operating system is probably not something that often comes to mind while playing. Nintendo systems have stuck with the A button throughout all of their various controllers and consoles, Sony came out the gate in 1995 with an unorthodox X button confirm in western regions while opting to go with the O button in Japan, and the Xbox controllers go with the A button but in the bottom position similar to the X button's placement on a DualShock controller.
Having owned and played various Sony/Nintendo consoles over the years, I have no problem switching between the two default confirm button placements. That said, subconsciously I feel a difference in perception of how some games feel with the A button versus the X button as the default confirm, jump, talk, etc. input. Like if I were to play a 3D Mario game with a DualShock controller and mapped X to be the jump/interact button, it'd feel really weird to me.
I'm probably just talking out of my ass in the midst of some non-drug-induced mania, but maybe someone else out there will relate to some degree.
I used to prefer the X button, but in recent years after spending so much time with my Switch Pro Controller I feel like that A button has become more natural for me. It just feels so right, y'know?