KW = all stainless construction (pretty with no rust)
HR = solid monotube construction with progressive damping characteristics
Both will do the job, neither has major high points over the other. The only thing I can say about the HRs is that they are have been tested over and over on the track and show their benefits every time. But that isn't saying the KW's aren't just as capable, just less products on the market to get the same feedback.