Hmmm... I'm not sure because everyone is different and there are so many bikes to choose from. I can tell you this will be my 3rd season riding. I started with a Ninja 250 and loved it and was very comfortable with the power and weight of the bike. Than I moved up to a Yamaha R6S after 6 months of riding. I made the jump too fast and never felt comfortable on the R6S like I did the Ninja. We ended up selling the R6S over the summer and we just bought a 2009 Ninja 250. I am going back to what was comfortable for me.
If you are a new rider I would truly recommend the Ninja 250 because its a forgiving bike that is easy to learn to ride on. You can always upgrade anytime.
Good luck with whatever you decide!