It doesn't matter much once your fingers get used to them and muscle's memory develop for the controller. BUT, objectively speaking; symmetrical is the way to go. Reason being is how you have your focus, it's generally why most NIntendo controllers have buttons symmetrical with the d-pad. It's also why they currently moved the analogue sticks in a symmetrical fashion. Focus is on both sticks now, it's no longer on face buttons or d-pads.