I've been a Snell Black player for a while, but recently picked up some MTB-X's when they were out of the Blacks. I hit the X higher than the Black, and it was immediately noticeable for me. Regarding feel, I think the Snell description is good..."slightly firmer". I actually like the feel of the X...I was expecting "clicky" and it's not. But I think the Black gives me a better ball flight so I'll probably stick with that when the yellows are back in stock.