Keens or Del Frisco
I would definitely go to Keen's. Del Frisco's has great steaks, but it is very loud and full of corporate suits, so I don't think it has anything on the one-of-a-kind, old New York atmosphere that Keen's offers. And you won't be taking a lesser option on the food either. Keen's also has great steaks, but the mutton chop is one of the best meat dishes I have ever had.