On a route that long, I'd definitely recommend Premium Economy. The extra leg room and seat space, not to mention the separate cabin just makes the whole flight so much more pleasant.
I've only flown to HK on the evening flight, but the evening arrival into HKG is pretty good for the body clock, as you are already tired after the flight so by the time you have got to your hotel, you are ready for bed and can start early and refreshed the next day without wasting any time.
