I think Kentucky would be a better place for Petrino. Auburn is not in a good position right now. A&M looks good, and Auburn is well behind Alabama and LSU. He would get fired at Auburn, for a season that would give him job security at Kentucky. He's not a bad coach, and I think he could get Kentucky to a bowl game most years. Not much better than that, but Kentucky wouldn't need much better than that.
I'm not sure how bad Auburn wants Petrino, or if they want him at all but Kentucky seems like a good place for him to settle for a while.