Using a 1-10 scale gauge is almost always limiting. It is best to break the topic into smaller units and describe/compare each component. Some components are more important to specific proprietors. Regarding cheese, some components are cost, salt content, browning characteristics, maintainance of appearance/texture over time, coverage, stretchability, and taste. Perhaps some others could expand upon characteristics they find important?
In my case, I didn’t like the way the Costco cheese browned. It transitioned from white to a burnt brown color almost instantly. I believe this is characteristic of many part-skim milk cheeses. Since this was the pre-shredded type cheese, the anti-caking agent cellulose may partially been to blame. Perhaps Tom L can weigh in on this browning?
The undesirable browning characteristic was enough to avoid the Costco mozz. cheese.
Being located in Hawaii, are you finding that Costco has much better prices on cheese then other distributors?