I wonder what the performance difference is when you're actually handling the errors though. I'd imagine that

    try {
       doThing();
    } catch (Exception1 e) {
        handleError1();
    } catch (Exception2 e) {
        handleError2();
    } catch (Exception3 e) {
        handleError3();
    }

Might be slower than

    Error err = doThing();
    if (err.code === ERROR1) {
        handleError1();
    } else if (err.code === ERROR2) {
        handleError2();
    } else if (err.code === ERROR3) {
        handleError3();
    }

Exceptions are best in my mind when they are very coarsely-grained, and error-codes best when you need to handle very fine-grained errors. This is certainly true in the code ergonomics, but I'd be interested in seeing if it's true for performance as well.