> what it is about a foreach that you think would do a better job than a syntactical for-loop

It depends on the language. For example, an optimizing compiler can optimize the shit out of a for-each loop, but can only go so far in a for-loop. For example, in a for-loop, you can "skip around" the indices, and even go backward after going forward, while in a for-each loop, it will always go one-by-one, and the compiler can rely on that fact. Even the CPU can probably optimize it better since the data access will be more predictable.