IMO, the XC is setup better for all around riding and especially woods/off-road than the SX. Things like 18" rear wheel, less prone to stalling, bigger tank, kick stand, tried and true chassis, valved better for "some moto/some off-road" than SX's stiff legs.
I got the new 07 KTM 250XC about a month ago as a woods only bike, but like it so much..... I'm going to sell my 06 Honda CRF250R as I have no use for keeping it! The KTM does everything so well. Never thought I'd say that, but it's true (for me)! :cool:
BTW, I ride moto mostly during the week and go woods once or twice a month if I'm lucky.