All forums seem to have debates pro and con on covers. Some say they rub and damage the finish but I haven't found it to be a problem. They are a pain to install and remove. If you live in a very wind prone area, it might move more and cause damage. The biggest negative to me is they only last (me, at least) two or three years. The side material is soft and kind of fluffy, and will eventually tear. Usually at a seam. My unit is under oak trees which rain down nasty stuff in the spring so I think a cover is worth the cost and hassle, especially since we don't do weekend getaways. Others will not agree.
Unless you really enjoy cleaning and waxing, some kind of protection is useful. And any unit will look better longer, require less work and hold it's value better if covered somehow. A concrete floored barn with power is the gold standard.
You pays your money and you takes your choice. You can look up a lot of threads on various forums debating covers to help you decide. Best of luck on your research.
2015 Crossroads Cruiser Aire CAF27RL, 2018 F250 diesel crewcab SRW 4WD short bed, Trailer Saver hitch with Reese adapter on Ford OEM underbed 5th wheel connector.