Also, I don't know what my financial aid for Yale will be like yet. Thanks for the help guys.
I think I'd be 50/50 too (but with $$$, definitely Chicago). The Yale System is much different than the Chicago curriculum...keep that in mind. And, although UChicago isn't exactly located in the best area of the Windy City, you are a quick ride away to fun parts. Chicago >>> New Haven imo. I've also heard some negative things said about Yale's hospital...mainly that it's a much different experience training in a smaller New England town than it is training in a huge, diverse urban center. Chicago is building a brand new hospital (largest in the world) that will be where you will be doing M3 rotations. That sounds pretty awesome to me.
Given full tuition to Chicago though... I think it's a hands down winner. You'll have equal opportunities coming out of both, and Chicago is sort of riding a huge increase in the rankings and prestige. Yes, Yale students match really well...but I think the Chicago match list is almost just as impressive. Match will be largely determined by your Step Scores and how well you do in medical school rather than where you went for it.
Choose the environment you'd see yourself being happier socially, academically, clinically, etc. You wanna be at the place where you think you'd be most successful. Keep in mind the money...because seriously, you will be kicking yourself 4 years down the line if you end up choosing a much more expensive school just for a seemingly insignificant bump in "prestige".
Regardless of what we think now as pre-meds, the name of the institution you go to won't matter much once you get there. You'll be worried about learning the material, passing boards, gaining clinical skills for your future patients, paying down debt...maybe even getting married, starting a family. You won't care as much if you go to the #6 school or the #13 school. Just that you'll be passing at that #6 or #13 school.