Sometimes language is a limiting factor and so you need to change languages before getting better. However this is rare.

Is the trade off here having more secure code in exchange for added complexity/difficulty? This is a real question, has the Tor code itself been exploited by bad actors before? All the incedences I've seen in the news were some other software running over tor that would be exploited to phone home or give up user data.

Isn't this just the same value judgment mistake? You're just presupposing that things like "smaller code base" are better in virtue of themselves the same way that "rewritten in Rust" might be as well.

The parent poster's point is seemingly to reject "this is simply the better thing" (ie: "small code is better") and instead to focus on "for what we are doing it is the better thing". Why would "basic" profiler use be better than "niche" or "advanced" profiler use if for that context basic would actually have been inferior (for whatever value of basic we choose to go with)?

It seems to me that the reality we're often confronted with is that "better" is contextual, and I would say that "basic" or "smaller" are contextual too.

I think the chance that your Rust application is going to be more performant or efficient than C, is whether you are focused on writing performant and efficient code. Out-of-the-box, I’m guessing people will use too many cargo packages, each that are over-engineered or written by less-experienced developers, so it will be less efficient and less performant.

In addition, you could more easily inadvertently introduce security problems.

Is Rust the right choice for Tor? Sure. Is Tor the right choice for security? If they moved to Rust, they increased security risks to make it easier to manage and find help from younger less-experienced developers, so no.