I'm kinda a nut about keeping everything i own under cover. If i dint have enuf space for something to have a shelter from the elements, i wont buy it.
Dealers HAVE to leave their stuff outside, if its not seen, its not sold. They also wash their cars, etc regularly. And their turnover is fast (Hopefully). I recently sold my 14 yo JD tractor, and while it didn't sell immediately, everyone that came and looked at it asked me if it had been repainted ... it looked that good. Sun,snow,hail....they all take a tool on a paint job. I dint like to spend thousands on something then let it rot in the sun.
The wife and i have been looking for a new gooseneck horse trailer for some time. We finally found one we could both agree on, and it was 2.5" short of the length i had available for storage, and 1.5" short of the height i had available for storage....talk about a tight fit. Like i say, if it doesn't fit, i dint want it.
Short answer.....tarp is soso protection, and it will scratch the finish. If your weather isn't too harsh, those curved aluminum sheds make a good cover (anchor it to ground)...best bet- a nice shed with additional storage for implements,boats,whatever.