Congrats heythereman, I can imagine that choosing is difficult and time consuming. I only got into one school:-( But the funding offer is excellent (no TAing) and my potential advisors are brilliant, so I can't complain! My advice would be to contact 2 of your potential advisors' past students, one of whom who is in a tenure track job and the other who isn't. Ask them if they can recall any specific instances when advisor X provided support/encouragement...or didn't....
Re Columbia, I have heard that it is one of those places (like Chicago) where you have to be careful that the people on your committee get along. Otherwise, your work can became the staging grounds for a battle of personalities. Of course they both have outstanding faculty.
Best of luck to you in deciding! Any to anybody else still waiting!