Any updated recommendations on which flight is better from LHR?

I've reviewed this and other threads and sense that on LHR-JNB the 330-200 is newer than the 340-400, and better in J, as of a few years ago.

But what about Y, and in 2017? I need some clear and current advice, please.

I'd also be interested in loads. Would there be more space on SAA 235 or 237, generally? I'm thinking about my chances of either an empty seat next to me in Y, or a miraculous op-up to J (*A gold, though 100k).