The 1am flight would maximise daytime at both the origin and destination, and as long as you can deal with the jet lag, it allows you to get the most things done.

On the 9am, you pretty much lose the whole day in HKG as you wouldn't get to your hotel until at least 3-4pm. Plenty of time for a stroll and a nice dinner, however.

And then there's the afternoon flight, it has the novelty of possibly seeing 2 sunsets, although the best way to combat jet lag here would be to sleep as soon as you get on (or after the meal). And if you can get at least 8 hours of shut eye, then stay awake until landing, and crash as soon as you hit the hotel.