Taiwanese girls are far cuter, lady like and hygienic; Hong Kong ladies tend to be nice, but as the young get increasingly brainwashed, the day will come when HK girls in their 20's are a no go, as there will be little difference between them and farmers from the mainland. More mature HK ladies will still be all good for those that prefer older ladies.
If you really must marry a mainland girl, marry a rich one. Not because she's rich, but because she more likely to have open-minded, educated middle class parents. Ideally she will have previously studied abroad or is an entrepreneur that didn't need to get promotions on her knees.