Personally I am not particularly in favor of "beginner bikes" such as the 250's. It depends on the mindset and control you have, you could start of on a 1300cc Hayabusa with 200hp, but if you can constrain yourself in not doing any crazy things, take it easy and progress along the learning curve taking one step at a time. You shouldn't have any problems. I started out on a Kawasaki ZX6R 2001 model, which was fine for me. Looking back at it now I believe I would've been bored after several months or weeks even with a 250. Simply because it is good to have power available. And in some situations is even safer (Quickly overtaking others, etc.).
But in the end it all breaks down to the rider, if you're an idiot and act crazy, you will get hurt and it will cost you. That is something to keep in mind.
Also, as a beginner rider your insurance will cost quite a bit, simply as you havent build up any damage free years yet, be aware of that. Also bigger bikes in this respect will cost more than smaller bikes, as they are regarded as "dangerous" for newer riders, thus posing a greater risk (for the insurance companies) of having to pay out insurance.
But in my opinion, starting out with an older model (perhaps 90s) 600cc shouldn't be a problem, as long as you behave and don't overstep yourself (trying out the max speed on a straight road is fine, everyone does it, just be safe and wear your gear).
In the end it comes down to your preference, you should get the bike you want and dreamt of, and which you can afford. There's no point in getting a bike you don't really want.