I think we need someone like Marco to chime in on this one but I swear I have noticed a degradation in the quality of all the brands available to me (right now 5 brands) during these hot summer months.
Marco, anyone, am I crazy?

?
Still my favorite cheese, just not as high quality as winter/spring/fall. Could it be what the cows have to graze on is different in the summer? Maybe the summer months just screw up the cheese because of the heat and all the BS they must go through to get over here to the US.
Jeff, all five of the Italian brands seem to taste exactly the same to me. except one, and I have forgotten the name, but I will get back to you. The only buffalo mozzarella I would avoid would be the domestic ones. They have not tasted right at all to me the two times I have tried them.
Although my research has lead me to different conclusions you should definitely read this.
http://www.rurou.org/archives/000227.htmlI have found that my pizza is much better if I buy my buffalo mozzarella by the case wholesale where I can get it within a few days of manufacture. Believe it or not I then freeze my extra and that still turns out giving me a better product than if I buy at whole foods/trader joes etc. Obviously I don't recommend freezing it for ultimate flavor, but that is how bad it is on the shelves at most grocery stores. On top of that you can get HUGE discounts buying by the case.