Honestly it really depends on what kind of writer you want to be. I applied to Columbia and USC because I liked what they offered in screenwriting. NYU I checked out the school but I didn't apply because I didn't feel like the program fit for me. I got waitlisted at Columbia and rejected from USC so I wish I was in your shoes right now, congrats on getting into all three schools!
Really narrow down what you want to write about, and look at the curriculum of the school. If you want to do screenwriting and playwriting I would do NYU. If you want to do directing, producing, writing I would go to Columbia. If you want work on screenwriting only I would go to USC, they have classes like writing for Vampires and Zombies which just sounds awesome. Also it's all about location, CA and NY of course are the top places to live, but if you hate the cold or the city life you might be at a great school but hate your surroundings.
USC is
the school for film, it's the number one school in the country for film that helps you. I know Columbia is at five. Columbia was my first choice over USC because I love production as much as writing, and I really want to work on my skills as a director which is what you have to do for the first two years. Plus the staff and students were really friendly. I just felt the energy there. I didn't check out USC's campus and I am not a huge fan of California. So for me Columbia would be the best choice.
I wish you luck to be honest you need to look at each program and figure out which one is the best for you. Look at cost and even see which one is cheaper. All three are great programs, so I am sure whichever you pick, you'll be in the best of hands. If you don't pick Columbia let me know, lol!
Good luck
Looky Loo!