Based on my research before the purchase, I would have gone with Sv-650S, rather than Bandit 600S. My friend, however, sold me his Bandit really cheap, and my budget tipped the scale in this case.
My Bandit has a really bad buzz around 2500 rpm, which I guess is only noticeable when you stop-and-go. I also feel the buzzing at ~5000 rpm, though not nearly as bad as the other one mentioned. I really wish it had FI, because that 5 minute warm up and finagling with the choke is getting old for me. Because I gear up before every ride, the warm up is just an extra hassle. And if you try to get away without the warm up, you will be getting a nice adrenaline rush as you are clearing your first left turn, give it some throttle, and the engine acts like it will stall on you instead of revving up.
Overall I am happy with my Bandit. It is reasonably comfy, does pretty good on twisties and interstates alike. I wish I had ridden SV650 to know the difference, at least. I do know that Motorcyclist magazine can't stop ooh-ing and aah-ing about SV650, though.
Hope this helps.