As most gentlemen here pointed out, sharp is not enough. Smoothness is as important as sharpness.
That's what I was thinking when I started HADing. "Find the best, sharpest stone, and here you are". But somewhere along the way I noticed, there are plenty of old, and new, British slates, Jnats and others, that can give you that made-up legendary HHT6★ (6★, that is, if you blink at the hair and then look at the razor, the hair splits itself, spilling hair guts everywhere). But they were not smooth.
You can't enjoy a shave if it feels like you are sanding your face, even if it passes every test that exists for testing a sharp edge. Everybody prefers the edge that is so smooth, it seems like it doesn't even touch your face.
You have to try both of them to tell the difference. And, that smoothness part, like it's "grit", depends from stone to stone. Some are fine and smooth. Others, aren't. Personally, I think that, the sharper the edge-finer the stone, the harsher it will possibly be. There are always exceptions, but that's what I generally think for finishers.
So, if you are looking for a fine stone, go for a smooth natural, or, well, since I don't have experience with man made stones, listen to what the guys that have say.
And, you can buy experience! Buying a stone means testing it. Then, you read. Then buy another. After you understand what bevel is and how to set it correctly, compare what you already have. Then learn how to strop, if you are a HAD guy. And, there you have it, experience! What you don't like, you can always sell it. But not in a higher price than you bought it, that's the rule.