I don't personally know how the coating affects the sound of the cymbal, but I wouldn't imagine it'd be totally game-changing in the larger scheme of things.
As far as Zildjian, the only cymbals of theirs I'd vouch for out of personal experience is the K series. Haven't tried the blacks. You might have better luck on a drumming forum where there's likely to be a significantly larger user base of more personal experience with a lot of different cymbals.
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