I knew there would be a post like this. I'm not comparing the two by scale. But 9/11 was almost surreal, like a movie. Planes crashing into buildings and all that. It was more detached. You didn't see the individual human suffering- it was there, you knew it was there, but you didn't see it.
Hank Gathers collapsing was up-close and personal. It was a human being dying right up in your face. There was no filter, not even a sense of unreality. It was right... there.
That's just the way I see it. YMMV.