Well I'm not sure that there is a definitive answer to that one, as pasture, freshness, regions, breed of stock, health of animals, handling etc all contribute to the over all taste of milk.
I know that yield and curd formation, and eventually taste (freshness) is quite different when using fresh milk as opposed to store bought milk, but with the processes that store bought milk has gone through, we are essentially taking about two different products.
It is recommended that when pasturising milk that it be done in a double saucepan because too high a heat or boiling of the milk changes the milk proteins in a way that after adding rennent the milk maybe slow to set or not set at all. It is also recommended to cool the milk fairly quickly in a cold bath after pasturising.
I have pasturised fresh milk myself on occsion, and I can't say that there has been a noticable difference in the taste or quality of the final product.
Not sure this answers your question.