hmmm. i love M5 on my old YFZ600R. i asked for Z8 and PR3 because i heard that have better mileage.
for me grip on dry and on wet road are most important. i am not a racer, but i drive very impulsive sometimes, when i find a twistie road. and on higway i try topspeed every time.
if Z8 or PR3 have the grip near to M5, i will buy one of them, for better mileage. if not, i will buy M5.