A thing you might want to keep in mind is that even though CX might be cheaper than UA at times, the cheapest UA Y fares still earn you miles while CX doesnt.
You would need ~5 return USA-BKK trips to be able to keep CX Green after the changes in April if you fly on deep-discount Y tickets.
So unless you're willing to pay a little bit of a premium for V+ class tickets on CX there is no little to no use to the marco polo club.
I agree, event at that, since the modifications made to the MPC it's really only valuable if your flying in premium travel classes.