I would suggest that you choose the language that will stretch your brain the most. If you use this heuristic, don't completely ignore other obvious factors li

I would suggest that you choose the language that will stretch your brain the most. If you use this heuristic, don't completely ignore other obvious factors like practicality, availability on your platform, etc. But I think stretching your brain should be high up on the list. For me, this meant Haskell.