Decisions, decisions - anyone want to help?

Well, with the first marathon now under my belt, it's time to consider another one. So far, I'm looking at two: Chicago and Detroit. Each one has several personal pros and cons, but I'd like some input from people who have run one (or both) of them before making my decision. It may not influence it, but I do have to register in the next week or two in order to ensure a spot, and thought experienced runners might have some advice.