My wife is the better marksman (marksperson?) out of the two of us. If defense were a consideration in sleeping arrangements, she gets the spot closest to the outside door.
(As a practical matter, at home and when possible when traveling, we have separate bedrooms for sleeping. Her health issues, my snoring, our being on different sleep schedules, and my being a light sleeper all add up to needing separate sleeping space if we want any shot at good sleep.)