a) In terms of memory safety, Go is not memory safe in the presence of data races, and Go does not prevent data races at compile time.
On top of this Go does not enable ASLR on most OS's. That means that when Go loads code from other languages, such as C/C++, memory safety issues in those languages are extremely easy to exploit relative to in a language like Rust, which enables tons of mitigation techniques by default.
b) More loosely, Rust has a more expressive type system. It is, in my experience, much simpler to enforce constraints in a 'type driven' way. In my opinion, this leads to safer software.
As an example of (b) I have written authentication code that encodes the authentication protocol's state machine into the Rust type system. What this means is that it is impossible to jump between two states in an undefined way. Beyond that, because of Rust's affine type system, it is impossible to reference invalidated states.
For authentication code, especially when you add complex stateful transitions such as rate limiting, whitelisting, etc, this is an extremely effective way to reason about your security critical code.
I think there is a case to be made that there is a real, significant difference between the languages regarding security.
You could also make an argument about compile-time guarantees more generally.
I'm not sure it's really a great argument, but you could make it. I think the parent's statement that it's only Go because it's made by Google is demonstrably false.
