Kinda depends on which powder special you're talking about. From '98-2000, they are real close to the same chassis as the '01-'02 Mountain Cats. The plastic is different, and there is a very slight drop and roll on the chaincase on the MCs. I think it's worth a couple hundred bucks anyway. Plus they've got a little more power through the midrange due to the powervalves. I assume you're talking 600s, since that's the only motor that's common between the two.
Short answer, I think it's worth a bit more to have the newer sled.