Ok, the results are in. Two pizzas, one with part-skim Grande, the other with whole milk Grande cheese.
The taste panel consisted of myself, my wife, and two neighbors. The two pies were 100% identical except for the cheese. The dough was made as one batch then divided into two balls. The sauce came from the same jar. Both pizzas were cheese only.
The Grande whole milk got the edge as being more creamy and less salty, but I think it must have been a psychological thing because I then performed a blind taste test using melted mozzarella only. When the two cheeses were tasted alone (i.e. not on a pizza), the part-skim won! Go figure!
So, the verdict: Too close to call. Both the whole milk and part-skim were excellent. More testing is needed! Fortunately, I still have 12 pounds of the stuff in my freezer!