As a mere pax and very frequent flyer JNB-MUB, I have to say SA Air Link everytime! Sorry to sound negative, but all my recent experiences with Air Botswana have been utterly dreadful (lost luggage, cancelled flights, crazy re-routes) and they just couldn't care less. If you are really strapped for cash and can afford to arrive late (and probably without your luggage for a day or two), then risk Air Botswana but any extra expense associated with SA Air Link is completely worth it. Enjoy Botswana.