At least with the examples I have, my 'Surgical Black' hard Ark pocket stone is less aggressive and more a burnisher/polisher, than the translucent Ark I have (part of a tri-hone set). The translucent produces noticeably more swarf in sharpening, and is also less-prone to glazing as compared to my black hard stone. I've had to resurface the black hard a couple times, to keep it cutting at least some steel consistently. Even then, it's a lot more gentle in how it works, and seems to be the better polisher for steels suited to it.
