Well actually Doug, I don't do both at the same time, when I go home for winter/summer breaks, I take Yin Yang do, but during school, I take KSW. Many self-defense applications are very similar, however, I prefer the standing style fighting of YYD better, but the KSW grappling techniques are better i think. YYD is actually a combo of Korean and Chinese, more emphasis on the Chinese at first, and as you progress, there are more traditional, Ki-building, almost unknown Korean arts in the mix as well as some more Chinese arts.