So here's the inside scoop from a med student friend who lives in NY: The flagship program at Northshore/Long Island Jewish is the largest with ten residents per class (+2 prelim interns). They split their time between the two hospitals (both facilities are gorgeous), get a ton of OB volume, and serve a mix of more affluent patients at Northshore and a ethnically and socioeconomically diverse patient population at LIJ. Almost all, if not all residents are AMGs, and many from NY. Interns don't do C-sections, and surgical experience is limited until second year. Ryan program. Fellowship is very achievable from this program.
Lenox Hill is a smaller program, 4 per class, and has a more intimate, close knit community feel. Residents generally seem pretty happy. Almost all their time is spent at Lenox Hill Hospital and they serve a fairly affluent patient population in Upper East Side Manhattan. Almost all, if not all residents are AMGs, many (though not all) East Coasters. Lots of OB and GYN volume. Interns do c-sections from day 1. Most of first year is spent in OB, with little exposure to gyn/off service rotations. Not a ryan program. Fellowship is attainable from this program.
Staten Island is also a smaller program. Hospital is run down, and residents are not known for being very happy in their program. Mostly IMGs, some originally from NY. Patient population is very diverse. Not a ryan program. Most residents do general OB/GYN, though fellowship is possible.
Southside is a brand new program and my friend didn't have any information about it.