A friend of mine from the Chicago area recently visited Toronto for a few weeks. His opinion on the two cities were that Toronto was without doubt the better city. Toronto feels like a much safer and prosperous city. People are happier and poverty doesn't seem to be as much of an issue (I don't agree with him on that). He also said that Torontonians tend to care more about the well being of the collective, while Chicago and the United States in general tends to be more self centered (not sure if I agree with him on that either). In short, people in Toronto are more willing to help.
He did say that transit in Chicago may be better and that they have more "cool stuff" to see (this is changing). But if he had the opportunity to move, Toronto would win hands down.