The 25 is much better for jet lag as the arrival time forces you to wake at a more sensible point in the HK day. The risk with the 27 is that you sleep for 8 hours on board but wake early afternoon HK time and then have the mother of all battles to sleep that night.

The other benefit of the 25 is that the noisy dinner service is complete when you want to sleep. Despite the 27 leaving late evening there are always some weirdos who insist on eating at midnight when most of the cabin want to kip.

On the return I prefer the later flight as it gives you a slightly less uncivilised arrival. However as it is currently the 773 it is to be avoided in Club. Preferable in F however.