Putting a wider tire on the 250R will not give you "beter performance" it will only limit your "flickability". The widest tire you will be able to fit on the bike without modifying the swing arm is a 150... depending on brand you will have to figure out whether a 60 series or 70 series will work. There are lots of topics that cover this information... a little searching goes a long way. Good luck, let us know what you decide.
09' SE Ninja 250R
Shogun crash kit, Sato Racing bar ends, Pazzo shorty levers, Puig DB screen, Proton flushmounts, Luimoto seat covers, Fender Eliminator w/ LED signals and plate light, Progrip 725 black/green grips, Immortal Graphix Monster tank pad