sv's are GREAT bikes. i've owned ALOT of bikes over the years, and my '00 650 was a great track weapon, and a sweet street bike. the ONLY caution i can give you is that if you are the type of person that wants to rip mile long wheelies, don't go for the SV. (from experience, lol) they don't hold up to that well. anything on two wheels though, and they're awesome. mods are a-plenty too, and not expensive.

as far as the two bikes you mentioned, i like em both. the gsxr's from a few years back always felt bulky to me, but not so much any more. they've definately gotten slimmer. both the gixxer6 and the r6 are sweet bikes. my suggestion is to sit on em both, and see what you're more comfortable on. being comfortable on a bike makes EVERYTHING about riding it that much easier.