The exterior finish is purely personal choice they both have their own benefits. I agree with don0128 that delaminatation is not the problem it used to be.
If your camper is unpainted fiberglass you are going to have to stay on top of it with something to cut the UV damage. A good quality auto wax applied 3-4 times a year will keep your camper looking bright and shiny. If gelcoat is left unprotected you will have a major job to bring it back, you will need something to cut through the oxidation and clean it off, then start over with the waxing.
If you don't mind paying inflated prices for cleaners and waxes you can go to buy the "RV" or "Marine" products. I like my money in my pocket so I always buy that kind of product at my handy auto parts store.