If you are connecting on beyond HKG, here's another vote for the earlier flight into HKG. Twice in the last year we had to divert to ICN for fuel, so I would much prefer to have the extra time to connect. Assuming normal operations, you can then have the extra time for showering, etc.

If you are not connecting and don't have an early meeting scheduled in HKG, then go for the later flight.

I always go for the 4:30 PM flight on the return for personal reasons - see my wife earlier and to sleep in my own bed that night.