If you are paying only 5k more for Chicago, Chicago is a much better undergrad school. There is no guarantee that you will get into either of their medical schools which means you have to look at your opportunities coming out of the undergrad.
Pittsburgh being a state school, you do have to be a resident to maximize your opportunity of getting into Pitt medical school. Chicago does offer an inside track after third year to get into their medical school but I would assume the competition is brutal to get that option.
As a full scholarship holder, you will have better opportunities for research etc at Pitt and probably also have a better GPA. Pitt does push research opportunities with the medical school for the honors students very strongly. I noticed that top schools tend to get you a better MCAT score in the tradeoff than a state school (or do they prepare harder because their GPAs put them at a disadvantage?).
So do you feel like being a big fish at an average school or an average fish at a tough school?