If you're great in person -- much better than you look on paper -- an away rotation at a site slightly better than you might otherwise reasonably expect to match at might open a better door. But if you look good on paper and aren't guaranteed to impress on the wards, it doesn't seem to be necessary or even advisable. Don't aim so high that, even if you are great in person, they'll ignore you for a 'better on paper' Harvard grad.