khvzak has compiled some benchmarks. mlua and roto are some of the fastest: https://github.com/khvzak/script-bench-rs

Rhai is dynamically typed and uses reference counting, Rune has a full VM with a borrow checker, and Roto compiles to bytecode. The tradeoff is basically faster iteration with Rhai vs faster execution with Roto, with Rune sitting somewhere in the middle but feeling heavier.