Thanks for the nice detailed response.
Originally Posted by uastarflyer
You have it reverse - CX is AAdvantage, while SQ is Mileage Plus.
You are correct.
Originally Posted by uastarflyer
The answer to your question (if starting from scratch) is clearly Mileage Plus, since both SQ and UA both run non-stops SFO-TPE, no issues on mileage accrual, weird routings, etc.
Actually SQ does not fly non-stop to TPE. And UA has the same flight number but stops at NRT on the way to TPE.
Originally Posted by uastarflyer
What you have to balance is your "sunk investment" to date in AA.
This is the 64 billion miles question! I have about 400k miles on AA and can fly my family of 4 to Asia or South America using CX and AA.
Edited to add - you could ask to be comped to Mileage Plus Gold based on your Platinum with AA, and use these 4 trips to hit 1K...to even out your starting point.
I checked with the UA rep and he said I am about 4k miles away from reaching premier platinum which will give me 100% mileage bonus. Since you can't get comped to 1K (from AA's Exec Platinum) he suggested that I save this option for later. According to him this is allowed only once in your lifetime!