Al75 FYI. The Off Road belt has more teeth but only because the wheelbase is longer on the XXX-4 compaired to the XXX-S. If you are planning to run the offroad belt on the XXX-S, don't do it!
The extra length will give you problems when you go to use the belt tensioner. You won't be able to tighten the belt enough to keep it from slipping too much and scraping the tunnel, as well as itself, because of the extra length. That is not something you can just "dial out".