[jamesbritt]

This sounds like a trick question to get people to debate "What, really, is a functional programming language?"

And it is Shark Week. :)

The problem with your question(s) is that I don't know what your question really is. Are you asking for the pros and cons of Haskell and Lisp? Are you asking which is "better"? Absent any other info, we're left wondering "Better for what?"

Are you just asking if people usually have a hard time selecting any specific language for a project because there is a choice of languages that are both appropriate but different in interesting (and possibly significant) ways?

Anyways, absent any other details, I'm just gonna say Haskell. :)