For me, they’re similar enough that I can see what he’s getting at, although the price thing totally doesn’t hold out in Cape Town - there’s only one Vietnamese place I know of, and it’s pretty high-end, whereas there’s a lot more Thai places, in a range of prices. But maybe in a place with a larger Vietnamese population, it might hold.
An Indian restaurant near my house, closed a few years ago, used to make the absolute best (IMHO) Karahi Chicken. I was told that is more of a Pakistani dish. Any truth to that? Man, I miss eating that stuff. It was pretty spicy, but just right.