OpenBSD isn't materially more secure than Linux, these days.
They've shipped several RCEs over the years, in software included in base, but because the software is not enabled by default they don't update their security slogan.
It gives the impression of an OS that is free of vulns which is not true. The "default install" is not useful for much as IIRC it only has ssh enabled which means their claim of only two remote holes in $time_period is really just a claim against their TCP/IP stack and OpenSSH, not the entire OS.
They still are mutually exclusive. For example, you don't have built-in bitfields in Rust. You have fat objects that requires heap memory to work properly. Still, there are many kinds of metrics for performance. While the execution performance of Rust is fantastic that it reaches the figures on the ballpark with C and C++, and sometimes even better due to fundamental stuff like borrow rules and strong alias rules and immutability propagation, the developmental performance of Rust is abysmal at best :[ Bunch of concepts to understand, generic and trait bounds, async and Poll, crate orphan rules, ownership and lifetime and although my prior C++17 knowledge did help, but consider in the picture for a complete newbie, they are no easy feat to challenge.
The compilation performance of Rust is also unsatisfying too with right even though it got the package manager right. I remember sitting 15 minutes to build my first ESP32 RISC-V firmware in Rust and still have to wait 2 to 3 minutes for consecutive debug builds. All of that on a Ryzen 3700X, maybe machine issue idk.
... unless you need performance. What a vacuous statement!