My feeling is that NYC Chinatown has much better Chinese food than SF Chinatown, and man, I love SF, so it pains me to say that. However, you and I both know the best Chinese food in SF is not in SF Chinatown anyway.
If you are to swing by NYC Chinatown, then my recommend a small bowl of wonton from Noodle Village. It won’t take up much of your stomach space. 
I love the vegetables and fruits stands around Mott Street and other streets. They have very fresh vegetables and fruits. Some very good Lychees and (Chinese Wampi) 黃皮 can be found there – when in season. Just walking through (not buying) is a good experience for me.
There are a couple of good Dim Sum restaurants, but they are not high end Dim Sum like Koi Palace. They are very solid though. There are a couple nice Shanghai Soup Dumpling shops.
I went to Cha Chan Tang a few times. I like it, but I don’t love it.
I forgot if you love steam fish. If you do, you should try some steam fish in NYC which are difficult to find in the West Coast. The West and East Coast Chinese restaurants offer different fishes.
