The 01 SP as stated already has Fox shocks all the way around, it also has the exhaust valves. It's a nice sled with an excellent motor. The 01 XC is a very nice sled (I know my dad owns one) It is set up the same as the SP but without the Fox shocks all around. It still has the Fox PPS in teh rear though. The motor is stronger than the SP in the bottom end, same hp's in the mid range as the SP, and then the SP takes over on top because of the exhaust vavles. I believe it's only a 5 hp difference on the top end. I know the regular XC rocks and it's plenty quick. Stock it was faster than my stock ZL500, but now it's not.
Either one is a great trail machine, and I would lean towards the XC non-valved, as it's gets great gas mileage (14mph agressively ridden), maitence is very low (add oil, grease the suspenders every so often and ride) and the low end power is awesome.
But either way you cannot loose!
Mike
2000 Arctic Cat ZL500 - D&D Racing Can, D&D Clutching, Re-Jetted It, 120 Woody's, Various Appearance Acc.