I'm right-handed. When games were 0-2 buttons on either side I always held the joystick with my right hand. Right handers usually did in the 80s in my experience. It was when button amounts increased and 2-player cabs were standard that it made more sense to fix the joystick on the left.
It makes sense to mirror the button order as then you'll be using the same fingers. Your index finger nearest the joystick 'feels' like the first button.
It makes sense to mirror the button order as then you'll be using the same fingers. Your index finger nearest the joystick 'feels' like the first button.

