All of those schools have good reputations. In terms of postbacc, as long as you take the majority of your classes at a 4 year university, you'll be fine. Some medical schools might not look favorably if you took them all at a community college, making it difficult for them to gauge your performance. Your MCAT will tell them how well you learned your basic science pre-reqs though. So, as far as Loyola, UIC, or Northwestern....you'll just have to pick and choose what you like/dislike about each based on finances/location/profs/etc...but in the eyes of admissions offices (for med school), your grades and MCATS will say all they want to hear.