if u flying out with united .. then you will most likely fly out on an SAA flight, as they have a code share. Coming back would be either SAA or united flight.
Basically almost the same as SAA(I think) .... except our flight attends are generally a lot nicer

but i would go with delta as they generally cheaper ... also .... if you flying via JFK(always a parking lot with no bays) ... expect delays .. so that 28 hour flight ... can become a bit longer.
That price for SAA is ridiculous though ... you would def get a cheaper price if you go via a travel agent ... try flight center ... they generally cheap