Seems like a strange pair of languages to compare/contrast given that they are for such different use-cases.
The cognitive overhead of programming Rust need only be applied if you're programming systems or code that need fine control over memory. OCaml is a general purpose language with GC and much higher levels of abstraction that can be quite performant - or F# (for OCaml-like) or other mainstream ecosystems like .netcore or jvm that a much wider choice of libs than Rust. (And these also usually have a path to native or js and/or webasm.)
I really don't get the whole "rewrite it in Rust" thing at all, especially when 95% of those applications would be perfectly performant in a language that lets you focus on your domain, not on making the borrow-checker happy.
IMHO if your code is scoped to the lifetime of a call or transaction of some sort or has very simple allocation needs, then fine -- but if you want to have complex inter-relationships between objects and interesting data-structures in a long-running process then you're in for a world of hurt.
I really don't get the whole "rewrite it in Rust" thing at all, especially when 95% of those applications would be perfectly performant in a language that lets you focus on your domain, not on making the borrow-checker happy.
IMHO if your code is scoped to the lifetime of a call or transaction of some sort or has very simple allocation needs, then fine -- but if you want to have complex inter-relationships between objects and interesting data-structures in a long-running process then you're in for a world of hurt.