the xr is a trail bike while the crf is a motocross bike. XR is air cooled, crf is liquid cooled. XR is much heavier, CRF is light. they are completely different bikes. Both are good bikes, just depends on what you want to do.
correct! The last letter is the only true give away now, as in CRF230 "F" or CRF250"X" and CRF450"R"... R is for race and F is for fun or family and X is for crossbread I guess!