"Best in Class"

We often get asked to do "best in class" assessments or to design best in class solutions but who decides what this means? Who defines what's considered "the best"? What is it trying to answer or how does it support the underlying design problem? What do client's mean when they are looking for this, and how do we do a better job having discussions about before we scope? We may not have any answers, but we sure do have a heated discussion!