Jo'burg will be probably be the best one to come along on. As an Atco the RT procedures on that route would be more interesting at least.
Most importantly though it's a great social trip as we generally all go out for a meal and drinks plus golf/shooting/go karting during the day. Also the timings mean we can do this both nights as the check out is not until the next evening unlike Shanghai for instance.
It does actually cover 5 days though if you take into account leaving late at night on day 1 and landing back early on day 5. A Shanghai or Narita gets you back in the afternoon/evening of day 4.
Having said all that a Hong Kong is definately the most fun trip to come on socially. Unfortunately, as has been pointed out the crew would be carrying on to Sydney. If you could return with a different crew this wouldn't be a problem of course.
See you down route maybe!