I personally think the noon SFO-HKG is a completely waste of time. You loose the morning the day of your departure and you arrive at night (loose another day). However, taking this flight, you can enjoy a night's sleep before working the next morning.

Taking the night flight sucks if you can't sleep on planes (i.e. me). You arrive early in the morning and you still have a long day ahead.

It all depends on how you sleep and whether you want to rest immediately after your flight.

The return 2pm and 4pm are virtually the same.