i think the bottom line depends on which airline you expect to redeem the miles. if your free travels will be intra-Asia, no question stay with CX/Asia Miles. obviously this depends a great deal on whether you are an Asia or U.S. resident.

also if you expect your travel pattern to continue indefinitely, i say stay with CX so you get the perks on CX.

i had the same dilemna several years when i lived in HKG as an expat and decided to earn AA miles whenever possible. i think it was the right decision for me because i am a u.s. resident and expected my future travels to be on aa rather than cx.