It’s hard to compare across languages. Too many independent variables to consider. Take the example of grep vs Ripgrep. Is it fair to compare the compile times of grep written in C with ripgrep? I can see arguments both ways.

What I can say with confidence is that Rust build times have improved continuously in the last 2 years. It’s now 30-50% faster on common programs. The future is bright too, a new debug back end out in 2021 promises a further 50% improvement.

One of the reasons why it's hard to compare the two is that the standard metric is time/loc, and it varies hugely depending on which language features are used. Both languages have features that can blow up compile times by a factor of 1000 or more.

In my experience, cargo build (as of recently) is significantly faster than sbt compile (as of 3 years ago), but only a little faster than compile (as of 3 years ago) called from within the sbt shell.

This comparison is my gut feeling, on pretty small programs.