Mixed. Two admin buttons ('p' & 'esc'), the rest being button combinations. I do NOT use hardware shift/shazam, but I only use mame which doesn't need shift.
I started with all shift, but I exited far too many games by accident, an couldn't find a button combo never, ever pressed while playing without adding an extra button, but still let others exit when they wanted.
And
P1+P2 = ESC
is the
exact reason I started moving to mixed. Two player games where both players die at the same time resulted in exiting more than a couple times (and once is too many).
Nothing is worse then almost beating the boss, both you and your friend dieing, both trying to get back in the game, and BAM!! no more game, just a list of games, the one you just were playing highlighted, adrenaline still pumping but
no game to play. But the expressions are priceless; wish I had the set of pics of me and my brother the first time it happened.

WTF ...look at each other....

........

......... ARRRGGG!!!!
