620 is going to be better every time..but im guessing your choice is not purely down to commuting ?
S4R is luxury compared to sportsbikes, and the magura handlebars make for a far more superior riding position instead of forcing your arms into a position like your 620.
My clutch was heavy new but got better, and if you fit a 14T front sprocket then that improves things no end for town riding as like many ducatis, its a little overgeared as standard really.
Clutch shouldnt be a problem, but worst case, you can fit an aftermarket clutch slave cylinder (cyclecat, evoluzione etc) for about £70 which will lighten the clutch load by about 25%..
Hope that helps..and have you also considered joining
www.ukmonster.co.uk ?
Cheers & good luck
Nat
P.S Its a little early an im knackered so i'll take an espresso and a twix bar if thats OK with you..??
[Edited on 2-11-2005 by Nattyboy]