It's so rare these days that the visibility at the airport is more than 5km or so that it's not worth worrying about. 99% of the time it's just depressing to look out of the window at the blanket of brown smog that envelopes you as you descend towards Hong Kong.

Moreover with the new long haul business class your seat is facing inwards so it requires something of a contortionist act to look out of the window - it's not a position that I could comfortably maintain for any length of time.

Other than that, it depends in which direction the runways are being used. At this time of year the winds are predominantly from the east or north-east so 7R is generally used for takeoff and 7L for landing.

For takeoff, most if not all of the departures do a right turn off 7R once they get past the end of Lantau, so the left side would be most likely to get some sort of view of the harbour area.

For landing you won't get much of a view either way on most approaches since you come in primarily over the sea, but the right hand side might enable you to see the mountains of Lantau Island as you swing round them and in to land.

The approach and departure charts are here: http://www.opennav.com/airport/VHHH