You are wrong because you said above with China as the sole picture in your mind... but how about the other SEVEN nations, is no one comparable to VIE in terms of the land area, the population size, the size of the economy and the individual infrastructure needs?
There are also several issues to be considered when comparing infrastructure investment percentage:
1. Depending on the specifics, the infrastructure investment can be centralized or distributed. For example, spacefaring project is a centralized investment where there is really only one per nation. In comparison, establishment of elementary school for children is a distributed investment. So in this sense, percentage comparison is only effective for distributed infrastructure investment.
2. China is a technological provider and native manufacturer. This means for the same amount of investment, the Chinese will likely get much more in return since the cost of production is lower.
3. The companion point to point 2, of course, is the purchase parity in different nations. This is a complex issue, since domestic efforts will be using the native cost of material/labor, but if anything part of the project is purchased through international dealer, then much more complicated factors will set in.
4. Efficiency and corruption. Let's be honest, efficiency and corruption level can easily make or break large infrastructure project. We have seen a lot of examples around world that large amount money is thrown at a problem, but nothing actually got done.
Basically, China is a rather bad example for Vietnam to make any kind of comparison with. The two countries are simply too different and their technological level and industrial production capacity sit on very different levels. It is probably best to compare Vietnam or other ASEAN or African nations. (However, you need to exclude countries like Algeria, which is pretty much an petro-town.)
