if you think you're more likely to head into private practice, cancel U of C. if you're at all considering an academic career, cancel northwestern. just my opinion.
while northwestern definitely nicer facilities and an infinitely better location, i actually liked U of C a lot. very academic, with morning lecture before you hit the ORs, if you're into that kind of thing. of course, U of C also had the interviewer that repeatedly said to me, "It must be hard leaving your home program," during my interview.