The major difference is the RV or MC on the license plate. You do not have to pay for the expensive(over $100) MC plate for your SxS and you will have to renew the tags yearly. You can buy the lower priced($40) RV plate and then buy the OHV decal. The RV plate is a 1 time buy and the OHV is a renewal.
The difference in MC and RV is - MC 80% on road 20% off road, RV 20% on road 80% off road.
The RV is for those of us who just need to use the roads for a short distance to get from trail to trail - trailered to Bumblebee exit then off loaded then drive on the graded/unmaintained roads with a short drive on pavement in Mayer type of ride.
The MC is for those of us who live in Cave Creek and then drive it to Lake Pleasant and do the backside up to Crown King, then come down the front way and drive it back to Cave Creek on the frontage road.
The MC will also require an emission test later on, too. It will also require an Motorcycle endorsement on your driver's license.