Let me guess ... you used [a]

What are you implying? What should they have used?

The list datatype is horrendously unsuited for being used a queue. They should have used a datatype designed for use as a queue.

There are better pure queue types and STM channels and suchlike that are designed for the job, so if bench-marking then you want to be fair to Haskell and use the right type.

You should do a write-up on it and show your tests. As it stands, this post has almost no real value for anyone else and no one knows anything about what you used and how.