I can not say for all the industrial machinery and equipment (capital goods). But in some case, for example, D-19 diesel locomotive (Chinese) have become the main stay of our railways system, while we have a lot of problems with D-20 diesel locomotive (German), so the railways industry decided not to import them anymore. Very high price, together with not-as-good-as-expected quality of the German locomotive, high maintenance cost etc. were the main reasons. The same can be said for any equipment imported from the West. They may be (not always) better than the Chinese ones, but too expensive, together with very high maintenance costs and high-priced spare parts. That is why in Vietnam, industrialists are increasingly turning to Chinese, Japanese or Korean suppliers (I speak on Vietnam situation, which may be different in Iran, which locates closer to Western Europe).
In some cases, Chinese equipment proved to be very well-built, if you choose the right suppliers. But they can be of very poor quality, if you go to the wrong ones. Now even the US and Western countries have to import capital goods from China, I see no way that Iranian or Indian can not import them based on poor-quality stereotype.