Both have some advantages and drawbacks. I assume you're looking into the program in which NYCOM sends you to one hospital for the entire year. I have done a few rotations at NUMC, and my fiancee has done a few at Maimo. She thought Maimo was the most miserable place on earth to work, and that sentiment was shared by many of my classmates. On the other hand, I know of some who actively sought out that place for residency. She stated that the population is almost entirely minority and Orthodox Jewish, if you're interested in that.
As for NUMC, there is a tremendous amount of exploitation on the rotations, depending of course. They have a lot of specialties in which to work, and the atmosphere is generally more relaxed, unless you're made to do all the residents' consults all day while they surf the internet or discuss the latest Calcutta politics.