Slickrock RV is older but has the best tree coverage if you're looking for shade, also fairly close to downtown. Stayed there a couple of times, once in dead summer, and the shade was very welcome. If there for OHV running, you will need to trailer to the trailheads unless you have a street licensed SxS. Dirt "pads" and gravel/dirt roads.
Also stayed at Archview. You can ride OHVs direct from Archview to some trailheads. Archview is further away from town but is nice, I'd stay there again, it is newer so the trees are small, no shade. Has a community fire pit, small general store and attached fueling station.
For RV parks in Moab, it kind of comes down to what you are there for with regards to convenience.