Wow, I had forgot all about this forum until I got an email about this thread.
Stay away for a ss on your first bike. People will tell you, you will be fine a million times over because they did it or there brothers uncles cousins aunt did it and she was fine. They are the exception. Statistics show your much less likely to get hurt starting on something smaller.
There is no shame in the 250r, I loved mine. Wish I could of kept it. Last summer I put 5,201 miles on it before I sold it to a punk in NYC that totaled it.
They are awesome bikes, I weigh 175 and am 5'10" sure it was a little cramped but for a summer it was fine. Remember it's your first bike, not your last.
In March I picked up my second bike, the skills I learned on the 250 have kept me a live to this day. Unlike a ss, a 250 teaches you to carry speed in a corner and be aware of whats around you much more. If your not paying attention on a 600 and a truck comes barreling at your back you punch it and are out of the way. On the 250 you need to be aware that there could be a truck barreling at you. When I the highway, let the other person in your lane, don't pin it and expect to be able to cut them off. A 250 is still faster accelerating the 90% of the cars on the road but its better to be safe then preform a fly by and scare some moron who wasn't looking in the first place.
When hitting twisties with friends on a 600, you will be able to keep up once you learn to carry your speed. Body position means everything. Read Twist of the wrist vol. 1 & 2.
Like I said, I wish I could of kept mine but I do a ton of 2-up riding and that's where the 250 really died. In your first season, you shouldn't be doing any 2-up though, so it shouldn't be a big deal. Buy a used one, ride it, sell it for what you paid for it and move on.
http://www.youtube.com/watch?v=Mzp_TboNOSE