I have come to the following conclusions. There is very little open racisim in Japan and a fair bit in Korea. In Korea, you are paid quite a bit more than a Korean doing the same job but have to put up with the occasional snide remark. I always found Korean managers quite flexible once you learn how to deal with them. My teaching ideas were put into better use in Korea than in Japan.
Korean students win hands down.
Most are genuinely interested in improving their English. They are respectful and easy to teach. I spent a year playing silly games and acting like a clown. There is no doubt that Japan is superior in this respect. People are almost always extremely kind, even if they hate you.