Here are the results of running several Scheme implementations on a set of common benchmarks:
https://ecraven.github.io/r7rs-benchmarks/
A few years ago Racket switched to using Chez for its implementation. The lead for Racket (Matthew Flatt) seems pretty happy with the new Chez base: he and the team were able to reduce the total amount of code while at the same time improving performance. Here's the experience report from a few years ago: