Just out of curiosity, why is that? (With reference to the linked example, I mean.) Clearly they're in the same league, and so it's a close call. From my perspective, I like that Haskell reserved the single vertical bar for the list comprehension notation, so that it would be as close to familiar set-comprehension notation as possible. I also like how Haskell takes advantage of how the cons operator already implies in the pattern-matching that you're working with a list, and so the square brackets become unnecessary, whereas Erlang needs the noisy extra layer of brackets on top of the parenthesis needed for the pattern.
But once languages get this elegant, it's a close comparison. They're both beautiful to my eyes.