I wish I could say the choice of OCaml among all available functional languages was objective, rational and well-deserved... the fundamental reason is that my knowledge of OCaml is orders of magnitude greater than my knowledge of Haskell, F# or Erlang (three languages I would have considered using as well). I do find OCaml more adapted to the way I think, but the way I think probably ended up the way it is because I have been using OCaml a lot.

I can do a fairly adequate analysis of OCaml-versus-PHP or OCaml-versus-C# because I'm familiar with both sides of the equation, but I wouldn't be able to do an honest comparison of OCaml and Haskell.