[flohofwoe]

I think you should tinker enough with both languages to learn their main concepts and then let 'outside requirements' guide you from there. E.g. if you're looking for a C++ or Rust job, or want to contribute to a C++ or Rust open source project, or just generally enjoy one language more than the other for weekend projects.

Also, if you're already fluent in another imperative programming language, it shouldn't take more than one or two weeks of a few hours after work to get an initial grip on both languages and decide whether you like them or not.

Personally, I find both languages equally frustrating for 'spare time stuff' (for different reasons though) and prefer simpler languages like C, Zig, Go, Python or Typescript (depending on the problem at hand).