South Vietnamese ex-pats are not an especially unbiased source. (Consider the Cuban ex pat population, which again tends to be descended from people who backed the anti Castro forces. Not saying Cuba or Vietnam are perfect, but the people who flee a regime aren't the best people to assess it. Our strategy in Iraq was informed by information from Iraqi ex pats.) North, South, and Central Vietnam are traditionally distinct regions, yes, but the war wasn't between the north and south, it's just that the south started out occupied.
I've discussed this subject with Vietnamese, in Vietnamese, all over the country, including Hanoi. Anti-communist sentiment runs strong everywhere. People are smart enough to understand how much the communists have held back the development of their country.
