I'm having a very similar problem between Columbia and Case. The rankings are one thing: Like U MN and U Chicago, Columbia is ranked slightly higher than Case, but not enough to really matter. But like you, I am also certain that if it were just me to consider, I would pick Colubmia over Case because I just preferred the school, the city, and the teaching style (at least from what I could tell).
I'm still mulling the whole thing over, but I am sort of inclined to to the long distance route. I feel like I, personally, could be ok with a long distance relationship, and that the only thing that would keep me from doing it would be guilt. (And when I say guilt, I'm thinking more about letting down our family and friends than him. I think he would eventually be fine with it as well. But it's hard to shake external pressures.)
When it comes down to it, I'm not sure if guilt is a good enough reason. And I do feel strongly that there will always be a twinge of regret or resentment if I went against my own wishes on this very important decision.
One thing to consider -- and perhaps others can chime in on this. Would you be open to taking a year off? You may be able to negotiate things so that it wouldn't be four solid years apart, but rather two pre-clinical years apart (minus a summer after MS-1), then year 3 together. Plus, most schools seem to be fairly flexible for 4th year, so you could probably do rotations in her area and spend more time with her that way. And if she is also able/willing to take time off her program, it might just end up being less than 2 years apart. That, in my mind, is very different than 4 years.