If there are no substantial assets in HK and most of the assets are in Austrialia AND, most importantly, any children of the marriage under the age of 18 will continue to reside in Australia, then it would be far better to divorce under Australian family law.
For the lower earning spouse, divorce under Australian law is likely to be more beneficial in terms of any spousal maintenance award.
I have had a similar very messy case with divorce under UK matrimonial law even though my ex and children lived in HK. My ex was very 'smart' and moved back to the UK with the children (without my knowledge or consent) and filed for divorce under UK jurisdiction - effectively forum-shopping for a better divorce jurisdiction.
No HK lawyer wanted to get involved in a case involving a different jurisdiction. There is also the question of 'enforceability'. Easy enough to get a judgement against one party in one jurisdiction but quite another thing to enforce it in another jurisdiction.
Domicile and Residence are not the same thing, especially for divorce purposes but in the case being cited, Australia would be the best divorce jurisdiction, especially if the parties expect to continue living in Australia post divorce. It will almost certainly be more wife-friendly and will use a 50-50 split of assets to be a starting point rather than a finish point (although I believe HK matrimonial law does now recognise although not necessarily apply the principle in the English case of White v. White). The party with custody of the children will almost certainly retain the lion-share of any assets and be awarded the matrimonial home (assuming it is owned).
Discobay - how old are the children? Please tell your friend NOT to remove any minors out of Australia without the written consent of the father or permission of the Australian Family Court. Then it would really get messy. Assuming the children are under 18 she would be compelled to return to Australia with the children (unless an agreement could be reached out of Court with the father) AND get a police record which could go against her in any subsequent custody battle. This is becoming a big problem with international marriages which break down.