I think SBCL has better support for annotations. You can claim that a variable is an int and the compiler will thrust you and generante fast code.

You can use Typed Racket to add annotations. The compiler will verify your that your claims are consistent and perhaps add some runtime checks when you read data or use other external sources. It will remove most of the internal checks, but not all of them.

(Probably some features of Racket like impersonators make generating fast code faster, but on the other hand allows Typed Racket and other variants/libraries to ensure external objects behave correctly.)

Disclaimer: I use "Plain" Racket, so both descriptions may be slightly wrong.