I live in NW Ohio. This is a common topic in the General aviation community, and is where I draw my experience from, and the reason I don't use a cover.
Covers are very nice if used inside a hangar to keep bird crap, dust, and the occasional unauthorized looker from inspecting an airplane.
However, when used outside, they generally cause more damage then they prevent. The cover will collect dirt and moisture, and trap it. A loose cover that is flapping in the wind is the equivalent of #30 sandpaper and soon eats its way through paint, plastics, windscreens, windows, etc.
Care must be taken on sharp edges, so as not to damage the cover, which then flaps in the breeze, traps water and dirt, etc.
Critters love the new found home and create nests in pockets under the cover.
The big warning is, if you do decide to cover, make sure the cover is tight, secure, and nothing can flop in the wind.
A well secured cover will also make access to the MH virtually impossible without removing, then re-securing the cover.
The MH is designed to be outside, it should be able to survive Ohio's harsh winters.
Instead of a cover, do a good wax job on the MH to protect the surfaces from the winters blues.
1999 Fleetwood Southwind 35S (Ford F53 6.8L V10 275hp 4R100 4 spd trans) - Toad 2003 Saturn Vue.
It won't do MACH 2, but I can get a sandwich and take a pee.