It depends on your idea of value as to whether J is worth it or not, but the CX and KA J seat is literally the same on this route. One is red one is green. I quite like the hard shell Y seat as there is more legroom so would not be bothered if i got it on a 4-5 hour flight like this. I would go by schedule, and for me the CX outbound and KA return is the best.