Chicago or New York.
I will add that I have already been to New York and I enjoyed it.
Chicago looks good but it's smaller and i'm not sure there's alot of touristy stuff to do there. I would be worried that i'd have nothing toget up to. It's really cheap though, I can get a excellent hotel for my budget. The only thing putting me off it though is the lack of a dayflight. Last year I took the dayflight from JFK and it was fantastic.
I will say I hated the attitude of some New York shop clerks.
What do you think?