I preferred being able to work a full day on the departure date, a shorter journey-time, and arriving in HK near enough to bedtime.
The 777 / A380 differential exists, but it is overstated. Both are excellent.
For your A380 leg, go for an A or a K seat (slightly more legroom and stepped in from the aisle with a console between you and the aisle). This can be an issue for couples, but generally it means that the woman takes the one across from A/K as the shorter seat tends to be less of an issue.
Avoid the smaller cabin towards the rear of the plane. The much vaunted 23A/K is actually shorter and noise from the bar is a factor.
For your 777 leg, just nab a window seat and put your screen up.