Comment by crabbone

I would recommend neither of those.

Haskell has very bad syntax (with extensive backing from Microsoft, iirc the guy who writes the compiler is a Microsoft's Research employee).

F# is a straight-up Microsoft's language.

It doesn't matter what other benefits it has. Just don't touch anything created by that company, and you will have one fewer regrets in your life.

But, if you still want a language from that category: SML or Erlang would be my pick.