CX treats me much better as a LAN Emerald than LAN does. I was stuck in Y for a RT LAX-HKG trip (all others since have been in J or F). Although the flight was almost completely full, the girl at check in blocked the two seats next to me, giving me three across (lots of dirty looks from other passengers who were squeezed together). I was also greeted by name, given a bottle of water and first choice for meals. However, if I were you, I would go for CX Diamond if you can obtain it.