SAA business class on the 346 is great, especially the seat. You can make it completely flat as a 1.85m bed or slightly angled if you are taller. I had only night flights though last year and always slept very well.
Furthermore, JNB immigration is terrible (Had to queue for 1 1/2 hours once after arriving on LX F) and there is a walk to the domestic terminal through hordes of people who want money from you to show you were to go to. If HON arrival service can get you around immigration, it would be a great asset.
Never had a problem at CPT immigration, even though I had early morning arrivals. Should be even better in the evening, I guess.
SmilingBoy.