SA has more legroom
All the SA birds have between 33" to 35" in Y, which doesn't sound like a lot, but LH and SWISS have some of the tightest 31" seats I have ever been in. Just something to consider for the long flights.
I also noticed that the SA flights are consistently a little less full than the LH or SWISS flights when I have gone between Europe and Africa. I can usually get a middle section aisle seat and have an empty middle next to me on SA, while I have never had an empty seat next to me on LH or SWISS...could just be luck as well.
All Y food sucks, but I think SWISS > LH > SA.
SWISS and SA AVOD > LH AVOD
good luck with finding a good flight!