Just too much info you wouldn't get from a website (even if the input were to be totally honest...), like do the upstairs neighbours like to practise tap-dancing at midnight, is there a building site next door, is there a small temple downstairs where people are burning smoky incense 24/7, are there plumbing issues in the area causing Pongs and roadworks, etc., etc. ad nauseum.
Add to those the lack of consumer protection laws which means there is nothing to stop a major developer photo-shopping a complete district out of existence in their brochures (good luck if you're looking for West Tuen Mun in any of Sino's photos of Gold Coast, for instance), including photos of a flat totally unrelated to the listing, or including a plan with doll's house size furniture drawn in to give a fals idea of scale.
And the good places will snapped up within 24 hours, so hardly worthwhile listing them.
DO check out different districts before setting your heart on one sight unseen - lots of different vibes you won't get from the net.
ANother thing you will notice is that whole idea of distance in HK is different from any other big city I've known - only here would Ap Lei Chau be described as "outlying." I live about 45 minutes commute from Central and people consider it to be the Utter Ends of the Earth.