Originally Posted by
Thunderroad
One other consideration might be which US-based FF program you belong to, if any. If UA, you don't get the same bonus mileage benefits flying Star Alliance partner SQ in C or F as you would with UA itself. If AA, you do get those same bonuses on One World partner CX as you would with an AA flight. Also, if you're EXP in AA (or top status on other OW airlines), you get access to CX and other OW F lounges regardless of which class you fly. Not so with UA re its partners.
And Thunderroad has described the real key issue for me - the FF partner relationship.
CX to AA is a much smoother and more desireable transaction than SQ to UA.
CX to AA is much smoother information transfer (FF miles always show up) than SQ to UA (prepare to waste a lot of time trying to get credit).
CX to AA results in the class of service bonus and the EXP bonus. SQ to UA results in lots of hassle and limited bonii.
1W lounge access, exactly as Thunderroad states above, is better than *A.
I really want to love SQ, but they make it hard to do so. CX makes life a lot easier all around. All comparisons above based on SQ/CX F/J flight experiences in 2006, transpacific and regional.