I just got back into AMPS in the last 18months after years of mongering for Euros.
Below is just what I've seen. So if your experience is different, Im not trying to say others are wrong or that my word is absolute. My experience has been limited and is almost like a newbie. Just shooting my shots whenever I can. Sometimes I do a lot of research before hand and other times I've just found a local ad of made an appointment without any background.
In general what I've noticed is that K girls tend work at higher end places. C girls are everywhere accross the spectrum. By higher end I'm not talking 800hr I generally don't go over 320. Low end I consider the 40-50hr massage joints that offer extras should you care for it. In many cases the $50 house fee is indicative of the real massage being the service you'll probably want to stick to. I'll try to keep my notes on just the high end for comparisons sake.
I do find K girls to be prettier, and typically they stay more physically fit. The ones I've seen tend to have athletic builds and aren't just eating right, running and yoga to stay thin. It's not unusual to come accross a K girl that might be a little bit more tone and shapely.
Love the K girl tan. I do just love a tan on a woman to begin with, but love it even more on Korean, Japanese and South East Asian ladies. I've never met a C girl with a tan. I believe it's a cultural thing for them, milky white skin is their ideal. I think many would gain a point or two with a nice tan.
Plastic surgery is more of high end vs low end differentiator. I've seen as many C girls and K girls with lots of surgery all over the body. It's always the ones at the higher end that tend to have it. Since I've only seen K girls at high end places it's hard for me to say what the "norm" for a K girl is. Of non pros, I do tend to find K women more attractive in general without surgeries.
K girls tend to be a little more open and warm, personality wise. I've found that our cultures have just enough in common that jokes, complements and overall banter aren't lost in translation as much. As far as mastery of English, the K girls I've seen win hands down. Even if they can barely speak English they seem to have an easier time understanding and communicating, even when other means are necessary.
Demeanor is a tie. I've met more C ladies and have seen a variety of attitudes and such. Generally speaking C ladies are more business like even if they are good at the show for the session, especially the high end, they tend to be more mindful and strict about the clock and tend to have more limits. Not that K ladies let you hang out without limit, but if no one is next in line I find K ladies to be less bothered by the time running over. I wouldn't say this is a huge differentiator, just something I noticed.