HKG - LAX is my regular F route, I now only fly on HK based crew operated flights (usually CX 884 to LA and return on CX885 or 883 depending on my own schedule).

In my opinion, whether the day or night flight you can still get the 'full' experience. The only difference is just whether there's a breakfast vs. a shorter dinner service. Don't forget that if you are visiting HK, the evening flights (883/881) whilst get you in HK in the morning and you may have a full day in town, many hotels won't be able to check you in that early. Whilst the day flight out of LAX (885) gets you in HK early evening and you can still enjoy a nice dinner somewhere in town. I'd say choose the flight that suits you in terms of your own schedule/preference rather than trying to pick the flight that you can max out the F experience as either flights you can still enjoy the full F service.