Why does it have be one or the other? I think the two of them can be rather complementary. Julia does very well at calling libraries with a C ABI, and Rust can be used instead of C or Fortran, if you really need to (although, in over 3 years, using Julia to develop commercial products, I've not once needed to use C or Rust, as I originally had thought I'd need to, Julia has met and surpassed all of my performance expectations) I've also found that Julia handily beats any other language I've used (which is quite a few over 44+ years of programming!) at one metric that is frequently the most important to me, programmer productivity.