Redex's library selection is anemic compared to Crates.io, and so is Pursuit's. There are a couple of gems in both, but for any given use case it's just as likely you will have to write your own code than find a workable solution in the package manager.
More importantly, Rust has orders of magnitude higher bus factor than Purescript and ReasonML combined. Phil Freeman has long since left his project, and so will eventually Hongbo Zhang, at which point Reason will follow PS's slow downward spiral into open source limbo.
Believe it or not, I actually put a bit of thought into this. And I do firmly believe that Rust is by far the best ML-like language for the web available to the public right now. Perhaps I should finally write that blog post I keep putting off.