Umm... the M5 Guitar sounds very cool and "in the face". The API is a bit smother and easier to listen. P1 has more highs than the others and the sound feels a bit more hifi and not as tight in the mids/lows.
Bass is hard to judge cause the performences are very different.
Generally for modern sound i'd go with the M5 for oldschool the API is the way to go. P1 maybe for intro uses
if you want to make some more I'd suggest a bass comparison (only bass playing)
Some drum comparison with thight kicks and snares would be also interesting :D
Thanks