Well, Dusk and Her Embrace was my favorite until Midian. It is really close tho!
But overall I think that they had their best line up in Midian. While Nick is an amazing drummer and maybe even better than Adrian, I think that Adrian complements the bands sound better. The sound Martin adds to the overall atmosphere of the album is unreal and really amazing. I feel the album is the perfect balance between their old and new sound and it has no dull song in it, keeping you hooked from start to finish. I also love the narrations done by "Pinhead", he also does some in Thornography, his voice is very cool.