Cover it they are not hard to put or take off. I cover mine after cleaning and waxing and it still looks it when I uncover it. The cover also will help protect your roof and the items on it from any freezing and thawing cycles. As far as the cover tearing, cover anything sharp, I use pieces of pool noodles. Dealers can't possibly have covers or the time to cover every trailer they have and it would have to be uncovered to show them.
When I cover mine I lay the cover in my yard, fold the sides onto the roof. Then I roll the cover up, place it n the roof then unroll it. Then I just pull the sides down, tighten the straps and I'm done.