Regarding “fit,” remember that 1) it’s a continuum, not a duality, and 2) the happiness or satisfaction of a particular student and it’s correlation to “fit” relies somewhat on how adaptable that student is. Some people are by nature more adaptable and can be happy in any number of diverse scenarios, while other people need a strong affinity with their surroundings, environment and community to find satisfaction.
To the OP, you indicate a strong affinity for Vandy, but you have valid reasons to be conflicted and desire Chicago. If you are an adaptable person by nature, you will likely be happy at either school, and the stronger program at UC could bring a deep sense of satisfaction. On the other hand, if your not on the adaptable end of things, go for Vandy.
I also think intelligent people (I’m assuming you have some intellectual prowess, or you wouldn’t be faced with your current dilemma) have a tenancy to live in the intellect and disregard the heart. This often leads us to over analyze when comparing two things that are good. It’s easy to decide when the gulf is wide and the choice is clear, but we can propagate a never ending stream of pros and cons when two paths appear roughly equal, albeit different. It serves us well to do the math, but in the end, sometimes we need to go with our gut instinct. The intellect informs the heart and vice versa.
As a parent, and having some modicum of experience, your academic and professional future is not dictated by the school you attend. Does it have some impact? Sure, but I think it is less than many think. It especially becomes the splitting of hairs when comparing top schools. Rather, your own initiative and drive will determine your ultimate direction.
Good luck!