I was just accepted for the Loyola Post-Bacc program starting this August ('11). I only applied to Loyola after reading literally every single post on this entire website written about post-bacc programs in Chicago.
Between Loyola and Northwestern, Loyola's program (according to a lot of the responses on this website) seems to have a better support system. The pre-health office is apparently very helpful and they write a committee letter for you, which Northwestern may or may not do, I couldn't discern. Also, Northwestern was reviewed as not really having their house in order. I guess they haven't worked the kinks out yet, while Loyola puts their post-bacs with the undergrads so at least the pre-health office is experienced.
It really came down to a) I need a really strong support system because I have no idea what the hell I'm doing; I was an Econ/Art History double major, and b) I liked that Loyola's program was full time, which allows me to set a faster pace and get through this thing quickly even though I'll have to quit my job.
Hope that helps. Let me know what you decide, or you may have already decided.