I am flying NW on a Z fare LAX-NRT-ICN-NRT-PDX-LAX in January, which will put me within 7000 EQM's of Silver Elite. I am Platino with AM, but am looking to achieve Silver with either CO or NW so I can get upgraded on US domestic flights.

My main US airports are LAX & ATL. From Mexico to the US I fly out of BJX.

I would appreciate any inputs as to which program would give me the best overall odds for upgrades.

Thanks.