I chose Racket for a project that involved lots of AST manipulation. Those ASTs were already in s-expression format, so Scheme seemed a natural fit.

The lack of static types was annoying; Typed Racket helped, but was so slow I only enabled it during unit tests (more precisely: Typed Racket functions can be faster than those written in normal Racket, but calling them from normal Racket functions will be slow as it performs run-time checks)

https://github.com/Warbo/theory-exploration-benchmarks/tree/...