It's not just about bounds checks. I am way more agressive about borrowing fields of other types, particularly mutable borrows in ways that I wouldn't attempt in C to protect myself from future code from breaking invariants I'd have to rely on. This means I can write the hyper optimized version of an algorithm on any language, but I'm more likely to even attempt it in Rust.
An other bit I first saw observed by Armin Ronacher and which is indeed quite common is that Rust does not require you to be defensive (and pay the price) around protected resources e.g. you can hand out references to rc’d types or mutex’d, and you know it’s safe, if a bit constraining.
And so you save the overhead of the extra refcounting or the re-entrant locks (though that would be unsound anyway), and you can safely use anything which works off of references.
