I had both, the Kawi takes the cake, hands down. Not because of major performance differences, but I feel WAY more comfortable on the 6R. Not only is the ride position ight year's better, but it just feel's more seated in corners and under acceleration.
As far as mods, I've got a Muzzy slip on (no re-jet), and dropped a tooth upfront (much better), other mods are namely cosmetic. Haven't had any problems yet, so...