First off welcome to the site 
I can tell if was really cold this past weekend on Red, I can’t imagine trying to stick it out in a portable at least not overnight, I’d look for a rental or at very least a motel room for the overnight. Check the URL forum for more info.
Given the choice ( I wasn’t) I’d much rather fish Rainy, always have a of chance of catching the fish a personal best walleye, not sure there is a great chance of that on URL, for me I wouldn’t think twice I’d head to Rainy.
Good luck lets us know where you go and how you do.