Shit, I can answer this.
Thai-Thai women tend to be very professional, they're about their business. They don't really offer extras though outside anal. However you'll get the standard service you would anywhere else. Thai women also know how to do nuru. As far as looks go, Thai women can vary. They come in different shades, from dark to light. Even their body types have some variety. I've seen Thai women with fat asses. Though fit is more common. Nowadays Thai girls are covered in tattoos and have fake boobs. Nonetheless, they're a good fuck. They're easy to get along with and can be fun.
Vietnamese-Vietnamese women tend to be all natural. Although fake boobs isn't out of the question. Nowadays the young generation are getting tattoos and dying their hair blond. They usually come in two body types, fit or chubby. For looks, Vietnamese people tend to look a bit East Asian compared to their SEA counterparts. They're light skinned with black hair. A Frenchman once told me that Vietnamese women have the best boobs. I'm not sure I entirely agree or disagree on that assessment. Vietnamese people are actually not bad at English. Don't be surprised if you're able to hold a conversation with one. Out of K, J, C, and T girls, Vietnamese women have the best grasp of English. Performance wise, Viet girls are about their money and tend to be down for whatever. Though ymmv when it comes to anal, rimming, and bfs. I'd also be surprised if you could find a Viet girl that knows how to give a good nuru. Viet girls know how to have fun while on the job. If you take care of them, they'll take care of you. If you can make them feel good, it'll change the vibe and menu of the session. Like Thai women, they're easy to get along with as well.
Now where to get these girls in NYC is something I can't help you with. There's been a small uptick in Viet women coming into the city. So if you're interested, get them while you can. Occasionally one or two may pop up. Its not easy for Vietnamese people to get into the US. Same can be said of Thai women. I've seen less Thai women pop up in NYC than Viet women.