I would like to second the idea of AA/BA. I am pushing for AA EXP PLT but have been happy being AA PLT and BA Silver. I earned BA silver on my transatlantic flights but still have yet to understand better the tier system as I failed to qualify for 2004 though I dif fly 25k+.
Marco Polo seems to be stingy with mileage earned but then again, you get the better upgrade perks and can invite more guests with you to The Wing.
Other than that, I would go the AA route but do keep in mind, only YBH fares earn AA miles. This is okay when coming from the US but while working in Korea, I had some R fares intra-Asia on CX which did not count.
However, as OneWorld Sapphire like on AA, all flights out of HKG are international so you always get to the use the lounges and your miles earned are worth more with the fare sales offered on CX for AA members.
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Going back to the bAAsics