Currently, there is a glut of Chinese gals in NYC and accordingly, I'd say that all things being equal, on average, you will get the best performance from a Chinese gal. Historically, though, Koreans dominated the midtown market at a time when GFE-service was harder to come by. So, if you come across a Korean MILF, she may still be old school with her level of service but most have gone GFE to stay relevant. Real Japanese gals were a rarity in NYC up until fairly recently. Now, they are fairly common and the current crop is generally great on the service (and often in their 20's).
So, in terms of level of service -- currently I don't think that there's much of a difference. On pure attractiveness, I tend to prefer Koreans, though I agree with
@AppleRules that Koreans are (on average) often more "visually polished" than their other East Asian sisters, though not necessarily prettier. For me, my earliest Asian gals (both pros and "real life" girlfriends) were Korean and I, in fact, lived with a couple over the years, so I guess that I have to admit to a bit of personal historical bias for Koreans.
Objectively, though I think that as long as she's hot, willing and has a sweet & sexy attitude, that's what counts and you'll find the right gal for you irrespective of her ethnicity.
As far as Latinas -- my mom was Cuban so I grew up with Latinas with her side of the family -- here are my thoughts. I've also dated a few and also seen a few professionally. Latinas cover the gamut with various subcultures. You have the strong Afro-Latin influence with Dominicans and Puerto Ricans but a near pan-European influence with Argentinians and Uruguayans. And most of Latin America is mixed with the indigenous American peoples, languages, dress, etc. So, here too, it's really hard to pigeon-hole the "typical" Latina working gal. That said, of the relatively few Latinas I've seen, some are very, "anything you want papi" and some seem like Marta from the film Scarface if you somehow unknowingly insult them.
