What the wise man above said. If you don't need a 600 and your riding can keep you in 250-300 territory I'd consider strongly getting a supermoto.
After riding one for a month I sold all my sportbikes because the supermoto suited my riding needs much better. They have clear weaknesses for certain types of riding but I don't see much a 300cc p-twin will give you over them besides a slightly higher top speed and wind protection.
Supermoto will win in nimbleness, overall utility, and fun factor. Oh and they're way cooler looking