I don't have hard numbers on me at the moment, but I remember it going from roughly ~2-4s with Highlight.js on some poor file cases down to ~500ms with Syntect. From what I remember, Pygments was better than Highlight.js by a factor of roughly ~2x, but with Syntect still outperforming it significantly in the general cases.

I think Syntect is faster in general just because of the nature of the work (syntax highlighting is basically just a stack machine + running regex 24/7) and Rust being a really performant choice for this in comparison to Python/JS (although I am sure some less idiomatic code could improve the perf of a Python/JS implementation).

Hopefully one day I'll do a proper write-up / blog post on this topic and provide some more hard numbers / stats for everyone. :)