If a 600cc sport bike will fit you, frankly, so will the Ninja 250. The ninja is a more relaxed position than most modern 600cc sport bikes.
The answer is of course, sit on as many bikes as possible. When sitting on sport bikes, remember: Your hands are NOT supposed to support your weight. Your back/abs and wind have to support your weight. So think about that when sitting on them.
At 6’1″, you are an inch taller than me. I have a 32″ inseam and I find the cut out of the *new* Ninja 250 to be too low for my legs. Sit on it, see if you can comfortably grip the tank with your knees. If you can, you won’t regret that bike at all. Failing that, the 500 has more room for longer legs in the tank cut out, but still has fairly bent knees due to peg position (if your goal is a sport bike, no problem, that is relaxed compared to any 600cc sport bike). The older (far less sexy – and less expensive) Ninja 250 is also an option.
In regards to the SV650 Naked. I just took mine for a 30km ride yesterday (I’m moving up from a ZZR-250, very similar to a Ninja 250). The different in power and throttle response is HUGE. A small turn of the throttle produces a very abrupt increase in speed. Letting off on the throttle, even a little, produces pretty heavy engine braking. The 250 is a WAY easier bike to learn throttle control on.
Some people think the SV650 is a fine first bike. My experience says I would have learned much slower on that bike – it would not have been any more fun than the 250 for my first year. (Don’t get me wrong, I’m looking forward to it for my second year, but I have much better control than I did this time last year).
Don’t look down on the 250cc dual sports / super motos. They have a lower top speed, and smaller fuel tank (so less range), but they’l fit you very well, and are plenty fun. And despite the odd looks, they handle in a manner much like a proper sport bike (due to the high centre of gravity) which makes them a good learning ground for future supersport riders. The fact that you can ride down any road, of over medians and across the neighbours lawn is just icing on the cake
The MSF is a GREAT course. You’ll enjoy it. Don’t worry to much about shifting, you’ll pick it up pretty fast at the MSF.
Ride safe and have fun,