1) I don’t think that the law schools Justices attended tell us very much about them. Each school is diverse; students are only marginally impacted by their professors; and any impact is diminished by the decades of time passing after law school and before nomination. We see this on the current Court. Both Clarence Thomas and Sonia Sotomayor attended Yale within a few years of each other, but we don’t expect Thomas and Sotomayor to share a common approach to law because they both went to Yale.
2) I agree that there are differences, on average, between the kinds of Justices who were former appellate judges and those who were politicians or statesmen. But I think it’s hard to say that any one vote can be explained by any one biographical fact. At the end of his lecture, starting around the 57 minute mark, Amar speculates that Chief Justice Roberts’ vote upholding Obamacare may reflect the profound understanding of the federal taxing power that he would have acquired working at high-level positions in the Executive Branch. But I wasn’t persuaded. Drawing these lines among the Justices based on their resumes requires making some pretty thin distinctions. Heading OLC or being an Assistant to the SG doesn’t give you that appreciation, as the Scalia and Alito votes would indicate; time at the Counsel’s office or serving as Deputy SG does, as we would see with Roberts. Of all the factors that may influence a Justice, I’m skeptical that the details of these experiences explain all that much.