Timings are most important for me and the 787 flight lands in Jo'burg at 5.40am which is 3.40am UK time when the service commences in winter 2018. It doesn't make for a great nights rest.
I prefer a later departure and arrival, so on the winter schedule (both other flights are A380s in December), I'd take the 21h10 departure from Heathrow, eat in lounge, sleep on the plane, leisurely breakfast and arrive in Jo'burg at 10.15 (8.15am UK).