I've used both extensively, even on some similar projects. Biggest thing I've noticed with Rust is that—often by necessity—it's hard to design abstractions that

I've used both extensively, even on some similar projects. Biggest thing I've noticed with Rust is that—often by necessity—it's hard to design abstractions that don't leak implementation details. That's a fundamental property of how Rust uses its types to manage resources, and it can definitely pay off for some kinds of code with particular performance requirements. In practice, though, it also makes it much harder to write reusable abstractions, especially with anything involving first-class functions and polymorphism. The upshot is that the two languages feel very different, encourage totally different programming patterns and give you different high-level trade-offs. They're far more complementary than substitutable, and I expect my future projects will mix and match both.