Of the four, OG and Ping's are by far the better choices for food. Ambience is a little more bustling at OG - for whatever reason, Ping's is fairly quiet on weeknights.
OG = more traditional / Ping's = more adventurous. OG I tend to stick to seafood only, Ping's I'll do if there are going to be some land-meat dishes involved. A66 is decent, but of late I wouldn't put it in the top echelon for Manhattan Chinatown. Red Egg is more sceney, the food is... meh, nothing special.
Another place to consider is Fuleen Seafood - while well-known it's a little more "in-the-know" than the others, mainly on account of its location being on the "other side" of Bowery, in the part of Chinatown where the streets smell like fish and restos generallt cater a little more to locals. It's a big favorite of a lot of Western chefs. Fantastic seafood, as fresh as OG. Best to stick with saltwater fish & shellfish, though - which is a good rule for Chinatown in general. Great casseroles for cold nights (which Thursday might be) - the chicken and eggplant with salted fish is fantastic, and I love the taro root with preserved duck. They've actually been my #1 the last couple years (though the Chinatown rankings are always rotating...)