I think the wikipedia is pretty clear on the difference of the soy sauce, but I will give you little hints about Chinese and Japanese soy sauce. I am a Chinese.
I think you can categorize the soy sauce from the 2 countries by their eating habits.
Usually Chinese eats saltier cuisine, so their soy sauce is usually saltier, for example: frying, deep-frying, roast. The most common one is fresh soy sauce (生抽), which is saltier. And there are premium version for fresh soy sauce, for example, tóuchōu (simplified Chinese: 头抽; traditional Chinese: 頭抽) which claims to be richer in taste. Actually I think they are very similar in taste because the salty favour dominates your taste buds. Another kind of commonly used soy sauce is old soy sauce (老抽), which is less salty, sweeter in taste. Usually we use old soy sauce to give dark colour to cuisine so that it looks better. A Chinese old enough to cook will use these 2 kinds of soy sauce to combine the salty and sweet favour, of course, with the help of other things such as sugar.
As for Japanese soy sauce, I am not so sure about differences between all kinds of soy sauce. As far as I know, and from the Japanese cuisine I've eaten, the soy sauce they use is usually sweeter in taste. (of course not as sweet as candy) You can figure out the reason behind their sweeter soy sauce from their eating habits. Japan is surrounded by the sea which is a very good source of fish, shrimp and other seafood which is sweeter and fresher in taste than pork/beef. Japanese consume the most salmon in the world. In order to have a better taste of the seafood, some of their soy sauce may also contain fish and Kombu for sweeter and fresher taste. Yes, Japanese soy sauce is good with seafood.
By the way, tamari is a by-product of the fermentation of miso, which is an everyday cuisine for typical Japanese. The ingredient may vary in different manufacturers. You might want to check the label of your soy sauce for them. I think this conclude the rich in taste.