I use Rust instead of C++, but I also see my Julia code being faster than my Rust code.

In my view, it's not that Julia itself is faster than Rust - on the contrary, Rust as a language is faster than Julia. However, Julia's prototyping, iteration speed, benchmarking, profiling and observability is better. By the time I would have written the first working Rust version, I would have written it in Julia, profiled it, maybe changed part of the algorithm, and optimised it. Also, Julia makes more heavy use of generics than Rust, which often leads to better code specialization.

There are some ways in which Julia produces better machine code that Rust, but they're usually not decisive, and there are more ways in which Rust produces better machine code than Julia. Also, the performance ceiling for Rust is better because Rust allows you to do more advanced, low level optimisations than Julia.

This is pretty much it – when we had follow up interviews with the C++ devs, they had usually only had time to try one or two high-level approaches, and then do a bit of profiling & iteration. The Julia devs had time to try several approaches and do much more detailed profiling.