We are on Long Island, NY and have always covered our coach over the winter. As well, we when we were boaters we always covered our boats over the winter. A proper RV-specific cover is breathable (not “waterproof”), be made of non-scratching/scuffing inner material, and have several attachment points to ensure that it does not loosen or shift with the winds. Our cover has 14 cinch straps...under the coach and front and back that keeps it secure.
Over the years we have never had a cover cause damage to our coach’s finish. A cover best protects the RV from UV exposure, the elements in general, and keeps the coach cleaner come springtime.
At least that’s our experience and 2 cents. :-))