BigJimbo, regarding CX's economy class, for my mind it is superior in service standards, comfort, food and entertainment to both QF and BA. It truly is a class product. I have flown all three considerably and will always take CX given the choice. I've even been known to fly them even if it is not the most direct route.

As to which program to join to maximise points for your itinerary, I'm a QF FF and would say it offers you the most earning opportunities. You will be awarded actual miles flown (not 70% for discount Y or even 50% of actual miles flown), and all of your flights on AA in NA will accumulate a guaranteed minimum of 500 miles.

I'm not up to speed on other oneworld programs, but I think the Qantas program is up there with the best in terms of earning. Particularly if you are an Australian resident.