Reason is a syntax layer on top of OCaml, so it shares OCaml's production-readiness. The tooling that Reason uses to compile to JS (Bucklescript) was originally designed for OCaml, and Reason supports native targeting via the plain OCaml compiler backend as well. It's a pretty pleasant ecosystem at the moment.
In the same space we also find Fable, which hooks into Babel to compile F# to JS. We're using it in production and it's been surprisingly good. It's very nice to be able to share the definitions of data structures between the C# backend and JS (via F#) front-end.
ReasonML serves no purpose whatsoever. The syntax is worse than OCaml's (though, more regular) and the editor tooling is really awful. OCaml compiles to JS just fine.