I’m generally positive on rewriting openssl in rust, but agree the comparisons aren’t completely scientific or necessarily more important than correctness. First you should compare performance using the same implementations of cryptographic primitives as these are relatively easily fungible. We also don’t know if for example OpenSSL optimised primitives were used. Secondly the rust language only excludes memory bugs, it doesn’t exclude errors in the implementation of the tls protocol or incorrect usage of cryptographic primitives which can be just as catastrophic for security. These have been prevalent in OpenSSL and are somewhat harder to prevent a priori. For all we know these issues are worse for rustls than OpenSSL. This is where formally verified implementations would be useful.