The question is what sort of environment do you want to be in, Cody is a big enough place to have some amenities such as a decent size grocery store, a few things to do, etc. however it is not the most scenic part of Wyoming. I can't say much about Billings as I have only driven through, though I have spent a couple of weeks around Missoula, MT over the last 15 year, it too is a medium size city, a bit bigger than Cody, nice enough scenery, and seems to be where all the Hippies, and Hollywood movie stars retired to.