I've lived in both Chile and Vietnam, and Chile is light years ahead of Vietnam in every respect. I love Vietnam, but it has a long way to go before it reaches the standard of living of most South American nations
You cannot explain the difference in economy of those countries based on the ideology of their governments. Its more complicated than that. For instance, Chile is rich in agricultural and mineral resources and has less population than Vietnam.
Chile today is not Chile in 1980 say. And Chile did not suffer massive economic embargos arranged by the US for 20 years nor was it bombed by a superpower for a decade. (The US dropped more bombs in Laos -- which wasn't even technically a combatant -- than were dropped on Europe in WWII.) The amount of damage inflicted on Vietnam by the US is simply unprecedented. (And let's not even get into the "free fire zones" the US declared late in the war where it would simply shoot peasants and call them insurgents.)
Vietnam is currently accused by Human Rights Watch of having "over 135" political prisoners. The scale of human rights abuse in Vietnam, at its worst, is utterly dwarfed by those in US client states in South America.