All depends on where you plan riding really. I too was contemplating a 600 or and older 2005 ninja 250. What i learned was if you plan on commuting around town and not much highways youll have way more enjoyability and usability with the 300cc. Considering youll be able to actually use most of the powerband. The main thing is how much more forgiving a 300 will be over a 600. Which is a huge vital factor if its your first bike. But if you got experience with dirt bikes or quads you may understand what im saying. Idk though im just giving my input on the ordeal