I have a YZ250, and a WR250F. I'm at 165 lbs. on a heavy day, and love the WR250F ... but, I really do miss the light feel and extra snappy power I get out of the YZ250, yet don't miss the fact that I'm flapping around behind the YZ250 like a leaf in a tornado when I open it up. Then again, I wouldn't trade the way the WR handles and lugs the hills and handles the mud and tighter trails. If you are at 215 lbs., you may want to look at the 450, as I've found the limits of the 250F can be reached quite easily. I've often thought about trading the 250F for a 450F, but the weight of the bike versus my body weight has always stopped me from doing that, I just can't throw a 450F around like I can the 250F.
Good luck!
Roost