Could be several things:
1. When you were racing, were you losing by 1/2 a ski length, or could you fit a group of riders in-between the two of you. If it's real close, then yeah, it's probably the extra weight and rotating mass of the reverse. If it's a blow-out, then keep reading.
2. Are you riding stock for stock? Was the base model clutched, geared, studded, etc.? Adding a clutch kit will give it a bit more get-up. Studs will make it seem that way (Stock track doesn't hook up all that well.)
3. Do both sleds have all the updates done? I just got mine back from the dealer for the "cold start" upgrade. It included a new computer, and it has a noticable amount of power over what it had before.
4. How well is yours maintained? Do the clutches move easily? Is the chain properly tensioned with the correct amount of oil? Do all the bearings spin easily? Is the belt in good shape? Is the track tension to spec? (If it is, loosen it up. Spec track tension is way too tight.)
5. Icing. Did yours have a crapload of ice on it? Maybe the other guy closed off the tunnel. All that ice buildup can put a lot of extra friction on the track, as well as add a lot of weight.
I'd say just start comparing the two sleds and see what's different. If everything is the same except the model package, and there is still a large difference in power, then yeah, you might have an issue you should take up with your dealer.
