[lmm]

(For me Scala is the present - I've been doing it full-time for about 6 years now.)

Short answer: whichever you can get a job in. That's more important than the design differences between them, which are relatively small.

Long answer: I wouldn't use F# because nice as it is you're eventually going to want HKT. Between Scala and Haskell I'd pick based on your learning style - Scala lets you write familiar comfortable code and incrementally adopt functional features, Haskell forces you to dive straight in and do things the Right Way from the start.