DRUMMER CAFE

I think the K Dark hi-hats are less bright.
But Zildjian cymbals tend to vary a lot, so if you are in the market for either model you should go out and try a few pairs back to back.

I own the K Mastersounds in 13" size.

One thing that sets them apart is the ridged (wavy) bottom cymbal. I bought them specifically because I wanted a very pronounced foot chick, free of any chance of airlock. The waviness is not as wide or pronounced as Paiste Sound Edge hats I.e. not as loud either.

They've performed as expected. I do wish sometimes that they were just a tad more subtle but I'm glad they have presence when I need it. Guess I'll just have to buy more hats. 

The K Mastersounds are as Chris mentioned, brighter than the usual K Zildjian hi-hat.  To me they sound like the middle ground between regular 'A' and 'K' cymbals.

HTH

Jim