F# for ecosystem. Most stuff you’d need is available via nuget. Plus, interop with C# is trivial, so all of that ecosystem is there too. Ocaml has opam for package finding, but it’s a bit sparser.

That said, I don’t tend to use a huge number of 3rd-party modules, so it’s not a big differentiator for me. Too much of a liability to have dependencies on some rando from the internet: for work, we tend to stick to modules from trusted sources in the rare chance we use them (eg, Jane street).