An algorithm that's idiomatic in one language might be terribly unidiomatic in another. (I'm sure you know this, but) Haskell's pervasive laziness makes some algorithms tractable while requiring a lot of space/time complexity for other algorithms.
The benchmarks game URL was posted by someone who has put a lot of energy into promoting Haskell - dons makes the best of the opportunity that the benchmarks game provides to promote Haskell.
>>pervasive laziness... requiring a lot of space/time complexity for other algorithms<<
And GHC provides strictness analysis and explicit strictness to avoid reducing performance.
(Except for meteor-contest.)