When discussing post-metal we occasionally all climb WAY up our own asses. The genre comes with a pretentious sense of self satisfaction, for the fact that we listen to music we assume most wouldn't understand. It's not our fault we have a superiority complex. Blame the music. hahah.
That song just has the perfect blend, both equal parts of beauty and brutality.
If I HAD to pick a favourite....? I'd have to go album by album.
All I can think of off the top of my head is Backlit from Panopticon, and (like you said) Beginning and the End from Oceanic. I haven't listened to those albums in their entirety in a while, so when I'm done that I'll know for sure. hard to pick out individual tracks when they all blend into each other so well.
I was so disappointed when I saw the video that they cut the length of the song almost in half. Cool video, but ISIS don't need music videos. they make it very easy to come up with your own mental imagery.