Well, first of all Racket more closely resembles r6rs. The main large r6rs implementations (guile and chez) both have proper threads (guile even has a parallel

Well, first of all Racket more closely resembles r6rs. The main large r6rs implementations (guile and chez) both have proper threads (guile even has a parallel CML, which is probably my favourite way to do parallelism of all time) and a startup time measured in single digits (ms) compared to hundreds for racket and something like 80 for racket/base on my slow computer.