I can only really speak for CX (JNB-HKG). Benefits of First (assuming here the new products for all except the first 2 points):
- meals when you want them
- better food, much better wine
- a seat that's wide enough to read a paper
- a window you can look out of comfortably
- an ottoman so someone can dine with you
- sleep suit
- better bedding
- more space generally - you can comfortably watch a movie and have dinner served at the same time
- much nicer toilets (particularly on the 747)