If money is not a problem get the 300. Better power delivery all around. The 250 is more peppy while the 300 is more mellow but has more torque.
Heck, buy both and I will ride whichever one you dont like.
2010 Husaberg FE390
1996 Gas Gas JXT270
2007 Yamaha YZ250F
2007 KTM 640 Adventure