I too completed a SFO-SIN via HKG. I believe the smaller cabin does play a factor but regardless of cabin size it all comes down to crew attitude and motiviation. Motivation and attitude are something that you can't teach someone. They either have it or they don't.

On my many trips to SIN I prefer going via HKG as my experiences have been excellent as you mentioned. On my last trip on November 28, I had the pleasure of flying with a chief purser whom I've flown with for 3 consecutive flights over the span of 2005-6 and she seems to have her crews doing the right things. I don't know how active other pursers are but while she might be assigned to F she's usually walking around in the other cabins making sure all is going well.

As for your HKG-SIN flight those are operated by the SIN/BKK based crews which have received a great deal of praise here on FT. Some of them are former UA crew and some also happen to be ex-SQ crew. It has been mentioned a few times before and I also agree that flying UA intra-asia vs. non-intra-asia is like flying 2 different airlines. Don't get me wrong I still like my HKG based crews to/from HKG

http://www.flyertalk.com/forum/showthread.php?t=536373