Stick with a 250 or if you want even better get the 300r, its a great beginner bike, its cheap and you want have a problem with a slip on the throttle and end up crashing because of too much power. I don't know why people think a 600 if a good beginner bike, the 600's now a days are a lot faster and lighter to what they use to be. stay low in the cc department for now until you're familiarized with the concept of a bike and the asshole riders you'll embark on.
__________________ All this is just ADVICE because at the end of the day, you can do whatever the FUCK you wanna do.
You only die once right? I sarted on.a katana 600. Not the same as a super sport. But looking back it was not the best choice. Could have done worse, but a ss 600 is asking to get hurt or killed. Its the equivalent to a 600 hp corvette. You wouldn't get your learners license with that.