The large class size doesnt hinder education at NYCOM. It offers great competition, as our facilities are op for the number of students. We have 2 newly built, high tech auditorium for seating up to 320 maximum capacity (don't worry, 4 huge doors in case of fire. =).. )
We have streaming videos for 90% of lectures (the other 10% is because the instructor does not want to stream for whatever reasons). Our OMM is great, nice lab, and our teachers are fantastic... nicest people i've ever met.
I am sure UMDNJ is not that bad either, so its basically up to you. I am not sure of the 3rd and 4th year rotation at UMDNJ, but at NYCOM it is great.... and one of the best in my opinion.
If I had to pick between UMDNJ or NYCOM, I would go to NYCOM only because I love NYC more. I am sure at almost any school you attend, its what you put in. If you are lazy, then forget it... but if you're a hard worker... then im sure you'll succeed anywhere you go.