I ride my sv650s as a commuter bike and a weekend tourer, and I love it. I'm 6'3", the ergonomics make it uncomfortable after about 2 hours of freeway riding, but if I'm just riding around town I can ride all day and I'm comfortable. Freeway riding sucks anyway. It's got great torque, it's a very fun bike. If you're worried about the seating position take Seruzawa's advice and buy the regular sv650.
The FZ6 you should steer clear of, the motor sucks, I rode one and I was happy to get back on my own bike after an hour.
The ducati is by far the coolest, but not necessarily the best in all-round usage. Not as powerful as the sv650, and a little more uncomfortable. But maybe that's a worthwhile sacrifice.
The ninja650r is just dorky. Sorry to all you ninja650r owners out there, it's just my opinion.