Having written a moderately big project in OCaml which I tried porting to F# and later did port to Rust, to me Rust feels much faster to develop than either OCaml or F#, especially once you figure out the "core", adding more features is a breeze. Refactoring is also easier. Not to mention that reading Rust is much easier than reading OCaml and coming back to the project after a year feels very easy. I think that I have less bugs with Rust than with OCaml. And the end product's core ended up being ~3-4 times faster to execute in Rust.