>Going from F# to Ocaml tend to be harder since F# has a number of functionalities that are often used and do not exist in Ocaml (such as parallelism, sequences, active pattern, list comprehension, type providers, etc and a much bigger std)

The opposite is also true, F# does not have ppx, OCaml's object system, GADTs, polymorphic variants, functors, first class modules, extendable variants.