Without question, inside is best. I've been fortunate enough to have our unit inside all but one year. Every storm, rarely worry about hail, wind, tree branches, etc. No sun hits it, just collects dust that is easily blown off on the first trip out of "the cave".
When it's rainin' out, snowing, sleet, etc I can still work on the exterior if I need to or other things outside without any issues. Though there is no heat inside,it typically stays warmer than outside, sometimes 30 degrees warmer since it's next to a wall that is heated on the other side.
As long as the barn is sound, I say pull it in the barn and don't think twice about it. If need be put some Decon dishes around the camper. You should have no issues.
Computers manufactured by companies such as IBM, Compaq and millions of others are by far the most popular with about 70 million machines in use worldwide. Macintosh fans note that cockroaches are far more numerous than humans and that numbers alone do not denote a higher life form. -NY Times 11/91