I also got both MAFN and Redirection to MSOR.
Based on my experience at Columbia, let me share some thoughts:
MAFN: (1) class size currently is <=100, but I heard that the director is planning to expand, so this year 100+ will be very likely; (2) curriculum is very solid, theoretical, but the quality of some courses is not such good as those offered at IEOR. (3) You can take at most 6 courses per semester at the same tuition cost, and choose 2 of them as R credit(only pass/fail), which gives you great flexibility. Each semester you are able to take at most 1 course in IEOR, and 1 in B-School. And if you plan to graduate within 1.5 year, the last semester only requires a extended residence cost for $11,470. (4) Many MAFN students are doing part-time, though some are illegal, but there are 'unpaid internship' and 'fieldwork' choices for students to do that legally. (5) the internship situation is not good compared with last year. I only know 20-30 international students got summer offer so far, although there are still many summer opportunities in the next month.
MSOR: (1) class size: 180+, very large. (2) Except those MSFE only, MSOR students are able to choose any other courses in this department. There are numerous good electives available. They can also register courses in Math, Stat department and B-School. Flexibility is even better than MAFN. (3) placement is very diversified in various sectors: business, consulting, IT, data science, finance and even services...Most of them finally didn't go the QUANT path.(4) Career service is better, while there is almost no career service at MAFN. (5) Overall placement rate is not good. Summer intern offers in Finance sector so far are around 10-15 (biased, just heard from their students). MAFN's history placement results are better than MSOR.
This is what I know. I haven't decided because I have other applications awaiting.
I haven't applied to Columbia MAFN, but I've been looking into MSOR's electives and I like what I see... I'll be sending that paragraph soon enough for sure.