F# started as an Ocaml port to the CLR. In the end, they decided to port a subset of the language so you get mostly the same syntax, no parametrised modules which is a big part of Ocaml but in exchange you can call libraries from other languages using the CLR. Of course, that comes with the issue of being a second class citizen in the .Net family, albeit a very nice second class citizen.

F# have drifted a bit further since but not that much. It’s a nice language but it’s not really comparable to Ocaml at this point. At least, I don’t see many cases where people would have to chose one or the other. I think people know if they want the CLR or not.