I agree that Viet girls are pretty but equally mercenary. Don't expect GFE as all they want is your SGD. China girls will at least pretend to like you give some GFE. Viet girls when bullied will also gang up to fight, have seen this happen years ago in Joo Chiat during the heydays.
Money is all they are after and I have seen three Viet girls taking selfies in Changi Airport departure floor with wads of SGD$50s.