I just got my license this year, I took the MSF course at the DMV. Definitely worth the money to get that first bit of riding out of the way on somebody else's bike. It was only $50 and I got my license at the end and 10% off my bike insurance.
I chose a Ninja250 for my first bike. I'm honestly VERY glad that I did. It's providing me the opportunity to learn a lot of techniques, mostly different types of shifting, that you couldn't do on a bigger bike while staying within the speed limit.
Truth be told, it's really not all that often that I need to open the throttle on this thing all the way, it goes 0-60 just as fast as a WRX STi. I don't really see the point in a 600cc bike that you can almost never use more than 1/3rd of the throttle. Those 600s are definitely cooler looking though
Which brings me to my next point, check your insurance before you buy anything. I have very good insurance on my bike and it's $1700 a year. I got a quote on a 2011 FZ6 (600CC yamaha) and they wanted $7000 to cover it, that's as much as the bike costs!
One last note about the Ninja250. Mine is a 2007 model. They're very light and have lots of top end power, resulting in the 0-60 time of 5.7 seconds and a quarter mile time of 14.6 seconds. On the 2008 and newer models they redesigned it to look like the 600 bikes, and while it is an awesome looking machine it added a lot of weight and they also shifted the power band on the engine from top end to low/midrange to make it easier for newer riders. The end result is a bike that is a full second slower in the quarter mile. I've been told that the suspension on it is a fair bit firmer and sportier than the model I have, but I can't tell you for certain.
Not saying which one is better, just putting the info out there.
Good luck, mate and ride safe!