United Airlines: Frequent Flyer Considerations
Cathay Pacific: The Wing, AVOD, Flight Attendants who Treat you like a Human Being, Newer equipment on that route, etc.,etc.
And one thing I had forgotten about until reading the OP inquiry...
The really funky times for UA in Singapore
Unless things have changed, you arrive from HKG around 0130 and leave for HKG around 0530.