Having coded a lot in both OCaml (I used to lead OCaml Batteries Included) and Rust (I'm a contributor to the Rust compiler and stdlib), I believe that they have very different targets.
Rust is really, really good at systems-level programming, it has great concurrency, but closures are more restricted than OCaml and it doesn't have general garbage-collection.
OCaml shines to implement really complicated algorithms. Anything that requires symbolic manipulation/pattern-matching, for instance, or manipulating large graphs, or maintaining extremely complex invariants. Garbage-collection that just works is invaluable but it doesn't play nicely with multicore yet.
In other words, I believe that there's room for both in our world! I could see myself developing applications in which some components are implemented in Rust and others in OCaml.
Rust is really, really good at systems-level programming, it has great concurrency, but closures are more restricted than OCaml and it doesn't have general garbage-collection.
OCaml shines to implement really complicated algorithms. Anything that requires symbolic manipulation/pattern-matching, for instance, or manipulating large graphs, or maintaining extremely complex invariants. Garbage-collection that just works is invaluable but it doesn't play nicely with multicore yet.
In other words, I believe that there's room for both in our world! I could see myself developing applications in which some components are implemented in Rust and others in OCaml.