Hey! Congratulations on getting acceptances from both schools. I also received my NW-MSiA acceptance earlier this month, but I still haven't heard from Columbia so far. As a natural consequence, I have slowly started to mentally prepare myself for a situation wherein I eventually join NW's program.
The reasons that I have given myself to feel happy about attending NW (instead of Columbia) are as follows:
(NOTE: I am explicitly stating my bias for NW here in case it wasn't clear enough)
1. MSiA has a smaller class-size (~40 students), so that should allow for more individual attention. Columbia has a class-size of 150+ students.
2. Living in Evanston should be more economical than living in NYC, thus there's some monetary incentive to attend NW.
3. There's a tremendous amount of data regarding students and their salaries on the NW website, whereas Columbia doesn't provide such details about their cohorts.
4. The campus at NW is supposed to be spacious and beautiful (it is situated next to Lake Michigan). I'd prefer a spacious campus over NYC's crammed buildings.
5. Chicago is a 30min drive from Evanston, so I believe there will be ample opportunities to find noteworthy employers. NYC would've been great, but I can work with Chicago.
6. As other users in this forum have mentioned before me, Columbia's DS program has a reputation for being a cash-cow.
By the way, I hope someone creates a list of reasons why you should pick Columbia over NW just to balance things out lol. The obvious reasons would be Columbia's Ivy League tag, NYC's job opportunities, highly qualified faculty, teaching/research opportunities (TA, RA etc), and the curriculum's solid emphasis on core technical subjects.
All the best and let me know what you finally choose!