The ARVNs did ok but a lot of the problem was with their dispersal. As well as ours. Too many were based in the provincial capitals, usually for the financial benefit of the provincial governor.
The most important thing is we learned from Vietnam War is more than just battles and firepower, it involves coordinating politics and being adept to the local culture and politics of the people in country. Look at our approach in Iraq and you will see not only the network centric technologies but also the political/cultural sophistication in our military.