Murph has it right, at least from my experiences with M80s/M60s. I found M60s to be a little more forgiving for poor recordings allowing me to listen to them longer and louder, while the M80s just sounded great with everything except poor recordings which forced me to stop listening to a few songs at louder levels as they sounded terrible.

Jason
M80 v2
VP160 v3
QS8 v2
PB13 Ultra
Denon 3808
Samsung 85" Q70