We live in Chicago and my son is currently deciding between Vanderbilt and another school. We were in fact at Vanderbilt this weekend. Like many of you, I do believe in “fit” and so Vanderbilt is a very, very defensible choice. But I think this is a lot harder decision than some of you are suggesting. The OP stated in post #1 that “UChicago is significantly more prestigious, affordable, and has better academics.” My point is that OP didn’t just provide one reason for UChicago but three, all of them valid (although I suppose we could quibble about the word “significantly” since both schools are tremendously well respected).
The OP has a little more than three weeks to make up his mind. If he hasn’t visited UChicago, I would suggest that a visit could help him with his decision. I would also suggest that he bring his parents into the discussion, since they presumably are financing this education and may have some strong views on VU v UChicago.
If the $ difference is not substantial, I would suggest that the OP trust his instincts and go to the place where he believes he will be happier. But again I appreciate why the OP seems so conflicted in this case. Tough call.