I was extremely excited to finally experience CX F on 881 (see my thread here https://www.flyertalk.com/forum/cath...ess-first.html) and although I can't comment on 885 vs 881, here are my thoughts:
- Fly whichever flight matches your itinerary best. I personally enjoyed being able to spend more time in LA (being able to have dinner before going to the airport) and arrive HK at the start of the day.
- Manage your expectations. As exciting as it is to be able to fly long haul F, it is still a "flight" which you need to get from point A to B. The service and product just make the journey easier. That being said, this was by far my best flight I have ever experienced, and the service although not 'WOW', met and slightly exceeded my expectations.
- My crew was LA based. I am usually indifferent to service (having worked primarily in the service industry my entire career) so believe that you can have good or bad service regardless of where the crew is from. This crew was professional and was able to cater to my every need (I didn't need to ask for anything). I guess they could have been 'friendlier' but I don't believe that would've made my flight any better. It was already awesome.
- It's okay to show that you've never been there before. My crew definitely picked up that I was in F for the first time and although it was never addressed, they still treated me well and were not snobbish in any way. I asked stupid questions, "where do I store my belongings"?, took a lot of photos and definitely geeked out at times "caviar is the best!".
- Qantas First Lounge was kind of "meh". I'm glad I didn't go to the aiport any earlier just to spend more time at any of the lounges.

If none of the above really matters to you and you want to be able to experience day time (photos will probably come out better) then by all means go for 885. However it is IMO that regardless of which flight you take, you'll most likely enjoy it as long as you dont set too high expectations. Have fun!

p.s. to take advantage of Vantage Pass, I booked HKG - LAX again for next year but on 883. I didn't really factor in the day vs night, mostly felt that the time suits me best as I get into HK even earlier than 881. If I do actually end up going to LA (I booked it more of a place holder as I may fly to a different destination for my 2nd trip), I'll definitely try and use AM to upgrade again!