I´m going to Courant. I don´t think that job placement will be a major concern when considering those 3 programs. They all will prepare you very well I´m sure. At the end, when the rubber meet the road, all you need to do is ace at the job interview.
Now personally, I already have a masters degree in applied math. So, although the campus experience in Ithaca seems a nice opportunity to enjoy some nature and college life, I think that too old for that already.
So location really matters, and thus, I fell that the more time I spend in Manhattan, more connections I will be able to make in order to maximize my chances to get a job afterwards.
Big class sizes could be good or bad. It depends on you. I like talking to people and so a big class (ok, not too big though) wouldn´t be an issue for me.
Finally, consider your formation and if you want to follow it or do something different. I am an applied mathematician by heart and I want to pursue this further, so how can I not choose Courant´s program? I think that by now you got the point.