Dom, cant really comment on HK V Dubai except to say general consensus is HK is better place to live from people who have done both.
The biggest negative about this place is the wonderful pollution our Northern neighbours send down to us, this is not likely to improve any time soon.
The main expense here is housing, you can get somewhere decent in Tung Chung ( next to airport ) for 12000HKD/mnth, the same thing in Disco Bay will cost double that, if you see the 2 places you will realise why.
Central, all I know is you get something pretty small around the 12-15K mark. " Decent " is 3 bed 2 bath 1200sq ft, small is 1 or 2 bed 600 sq ft.
I have found most other things, food shopping etc to be no worse if not better than home ( Oz ). Public transport is great so you can save a packet not owning a car. Telecommunication stuff is dirt cheap.
If you are smart (ie., stay away from certain parts of central ), you can eat out really cheap too.
Sorry no idea on what Ops staff get, I would have thought you would want around 8- 10K hsng allowance? Tax here is 16% so take that into acct.
Hk very safe for families, kids etc ( except air quality ), but many people I speak to are happy to trade the air quality for the safety, especially for their children.
Hope this helps