Diversity and accessibility are the factors I consider most important. Diversity of faculty is difficult to attain. Most faculty members are lawyers who have worked long enough to gain a reputation in their field. This almost guarantees that they are white males, since that's what virtually all lawyers were until a few years ago, and the vast majority still are. The shortage of women and minorities on the faculty is multiplied by the problems they face in gaining a reputation in their field.
Accessibility is more difficult to measure.
Famous professors, authors of landmark treatises and litigators of great cases may not be as accessible as their less-pursued colleagues. But it can affect the quality of some services. I have heard of students waiting a semester or two to study with the professor of their choice. In those cases, the faculty are so busy teaching the basics that they aren't available for advanced seminars. Faculty attitudes are no more quantifiable than accessibility.