2002 and newer 700 - 128 HP (with exhaust valves)
2002 and newer 800 - 136 ish HP (w/VES) - I think
Non-VES 700 120 HP
Non-VES 800 133 HP (?)
Non-VES 700 w/ boost bottle, V-force reeds, exhaust canister, high compression heads - 133ish (per a Snow Tech stage tuning article for this motor).
The 2003 SKS's are a sweet compromise between moutain and trail because of the tipped up rails. Definately worth a serious look if you are wanting to have something of both worlds (trails and deep snow) but stay w/one sled.
All the numbers above aside, buying new, just give in to fun and get an 800. Yes, a little tougher on clutches but in the moutains, power is everything. On the other hand, saving 6-1000 bucks and sticking with a very capable 700 is not all bad either. Plus, a used 800 will hold it's value better. Good for the seller, bad for the buyer. Any anyone that thinks that 700's are for whimps will be (okay, might be) offered a ride on mine. It ROCKS !