The Most Brilliant Diamond in the World?

Is referring to your product as “the most brilliant” mere puffery, or a false claim? Zale Corporation, known for the Zales jewelry stores, is being sued for false advertising by Sterling Jewelers Inc., the parent company of Jared and Kay Jewelers, on the basis of this question.  Zales recently began advertising its “Celebration Fire” diamonds as “the Most Brilliant Diamond in the World.”  Some of the advertisements say that the claim is based on testing; Sterling argues that because Zales tested only a select few diamonds, they necessarily did not test all the diamonds in the world.  Moreover, the use of the term “brilliance” is different from mere puffery in that it points to a single characteristic that happens to be widely recognized within the industry.