When to use Primary cells and when to use cell line? Does Passaging change the primary cells' characteristics?

I am working with Bovine Aortic endothelial cells and in those cells we want to check the effect of growth factors on a particular gene at the mRNA levels. There are human primary cells available but I did not find any human endothelial cell line. I wanted to know what are the advantages of using a primary cell over cell line ( I know that cell lines are transformed and are a deviation from normal cells). Also, in terms of the experiment when should we use cell line and when should we check in primary cells?