Haskell is much simpler than F# in its full .NET multi-paradigm "glory" but moderately more complex than the fragment of F# used in idiomatic functional code.
Thanks, that's good to know. One of the things drawing me to learn Haskell is Higher-Kinded Types. I'd really like to learn about them and have a play.
Higher-Kinded Types seem complex to me but until I have a play I wont know.
The other thing that makes me think Haskell is harder is that functional code is enforced, while in F# it's simply the default. I'm not sure what impact this will have on complexity of real world applications. But in F# it's really easy to have an imperative shell and functional core.