FWIW, I've been told & have read, that D2's great for cutting & 1095's great for chopping. In other words, D2's "said" to be better for a smaller knife like the RAT3, where you'll cut with it more. 1095's "said" to be better for a larger knife where you'll possibly chop with it more.
D2 will tend to hold its edge better, but isn't as easy to sharpen (I believe because of its greater hardness, it'll be more prone for edge damage, such as from chopping). 1095 might not hold its edge as well, but it's easier to sharpen & probably easier to get a real sharp edge on it (Not that you can't with D2, but it's harder to do). I believe 1095 is less brittle, due to it being a softer metal, which is probably better for a larger (For chopping) knife.
Personally, I went with the D2 for my RAT3.