You should ask yourself what you would like to do after school, and where. While Michigan is ranked higher, NW is a very good school as well, and has excellent name recognition in the Midwest. In Chicago in particular, I don't believe Michigan would give you any particular advantage over Northwestern. Also, if you plan on staying in Chicago, Northwestern will put you in a good position to work relationships during the school year.On the other hand, if you plan on heading to the coasts, or to academia, then Michigan would probably make a difference - it has been my experience that Northwestern is very regional, and academic hires are very rank-conscious.
I assume you mean very regional relative to Michigan.