Harvard will help you get into med school due to grade inflation + fewer requirements.
UChicago will really make it harder for you as a premed (to the point it may kill your possibility of going to med school) but it’s a bit cheaper.
However, right now you’re talking about the Facebook relations built over the past 4 months as one of your main reasons to turn down Harvard, so perhaps you need to think of where you want to be 4 years from now and how much these past 4 months on UChic’s FB will really matter. You should attend UChic for what it is, its vibe and the core in particular.
Someone will happily be taken off the waitlist when you turn down one of these two schools. 
Don’t forget to post your decisions!