The wet clutch on the 750 has a smoother, more consistent engagement and will stand up better to nubee abuse. Supposedly less strength needed, though I don't see much of a difference on the 750. Noticeable on the 600 and 620 though. The only real negative is they are more prone to clutch drag when cold. Gotta say I do love my dry clutch though.
I had a 900SS dry and the clutch was I guess 'snappier' than the wet clutch on my M750. Also, I've got 45,000 miles on the original M750 clutch and I was putting a clutch pack in the 900SS at 18,000 miles. So they seems to be some wear differences for sure. I can't rule out rider error, but I'm 39 and have been driving with a clutch since 12 years old so I've not a clutch idiot.
Tune does make a difference, my M750 was jerky at slow speeds, the 900 was not, but some carb adjustments on the M750 really cleaned up the slow speed stuff. Sure it was definitely slower than the 900, but the M750 properly set up is pretty pretty much a smooth puller from twist to redline.
JM