which program to join?
 

I currently have an account with AA, but will soon have 20k mile itinerary coming up on CX in M class (NYC-HKG-KTM), which earns me 0 miles with AA. (Going up to H for earning miles is an extra $400, not worth it this time around).

So the question is then, where should I get these miles banked? It would be my secondary FF account, so I don't expect to earn status, but would like to maximize long term benefits.

Search didn't find me anything, let me know if I missed it.

CX - 100%
AY - 100%
AS - 50%, not tier qualifying

Yup, but if you're going to bank with CX, realize that the miles expire in 3 years. 20K miles, however, is good enough for some domestic trips, though I'm not sure the distance. You could double check on www.asiamiles.com