In that conflict in 1979, neither side went to all-out-war and the only thing that can be said is that the Chinese failed to get Vietnam to pull their troops from Cambodia. In an all-out-war, either in 1979 or now, the Chinese have to have the advantage, just by size alone. (And the Chinese have no Jane Fondas, then or now.)
But you have to hand it to the Vietnamese commies. They weathered the French, the US, and the Chinese... though with Soviet assistance in the last two and with a major failure of will here in the US, not to mention a lot of high treason on the part of many Americans. Still, the Vietnamese commies did hang tough through all of that.
“In an all-out-war, either in 1979 or now, the Chinese have to have the advantage, just by size alone. “
The Chinese have a huge numerical advantage but there’s a geographical problem that hinders their ability to use it. It’s difficult for them to funnel troops into Southeast Asia and Vietnam takes full advantage of that.
It will be interesting to see what Vietnam does if/when China builds a blue water navy able to move troops by sea. I’d look for them to come hat in hand to the United States.