Although I've never been to Vietnam, I'm very respectful of it as a nation, a feat which I'm pretty sure very common among my Indian brethren.
If they are ahead of us, I congratulate them. Whatever they have achieved its because they have worked hard to be what they are today.
Possible reasons for why they have developed better,
a) Authoritarian Government - faster decisions, low rate of inclusion of a whole lot of people in decision making.
b) Investment in Infrastructure and Education - They have invested good in these key areas, it has given them an efficient workforce with able infrastructure to fully tap the enhanced skills of its human resource.
c) After-war effect - The war-torn country had to start rebuilding its economy from the scratch. When you hit rock bottom, there's no other way left but upwards. Best examples, Japan-Germany.
d) Communism - Although Vietcong was supported by many in the South, the communist leadership of the newly united country still had to prove to many of its citizens who were in favour of Democracy that Communism can be equally good or can even perform better when it comes to economic growth.
Why don't you use China here?
neva gona happen bud, even if Vietnam is more developed than India, then we would acknowledge that fact,congratulate you guys and move on 
