First, consider the broad range of choices Obama faces. His shortlist consists of former law clerks to a wide range of the liberal Justices of the 1970s and 1980s. Obama must choose between a Brennan clerk (Garland), a Marshall clerk (Kagan), and a Blackmun clerk (Wood). Further, the shortlisters differ dramatically in that they had different high-level positions in the Clinton Administration. Will Obama pick the former Deputy Assistant Attorney General for the Criminal Division (Garland), the former Deputy Assistant Attorney General for the Antitrust Division (Wood), or the former Associate White House Counsel (Kagan)?
Even if Obama decides on a former academic, he has to pick which kind of resume he wants. For example, does he pick the woman who was a full-time law professor at the University of Chicago from 1981 to 1993 (Wood)? Or does he pick the woman who was a full-time law professor at the University of Chicago from 1991 to 1995 (Kagan)? Obviously, these are big choices.
No matter who he chooses, Obama will continue to break new ground, or at least help bolster some of the low numbers of people of certain arguably underrepresented backgrounds on the current Court. For example, Elena Kagan would become only the second former Harvard professor presently on the Court (joining Justice Breyer). Either Kagan or Wood would be only the second Chicago professor (joining Justice Scalia). Further, Merrick Garland would be only the second Justice on the Court who went to Harvard College; then Harvard Law School; then clerked for Henry Friendly; then clerked at the Supreme Court; and then worked at DOJ and was a partner at a big DC law firm before serving on the DC Circuit (joining Chief Justice Roberts).
Elena Kagan would also bring notable educational diversity to the Court. Kagan would be the very first Justice ever to have attended Princeton and then Harvard Law. Obviously, that would be a major break after two consecutive nominees who had attended Princeton and then Yale Law (Justices Alito and Sotomayor). Whoever Obama picks, I think it’s clear that Obama faces a major choice and that his selection will be a historic occasion.
Reading through the recitation of the trio's clerkships, I still thought this was serious -- I was imagining some in-depth discussion of the different branches of liberalism represented by Justices Blackmun, Marshall, and Brennan. Alas, I was met with sarcasm instead. Albeit funny sarcasm.
However, Professor's (fully-warranted) snarking aside, I think there are some significant choices inherent in the Wood/Kagan/Garland decision. First, in terms of relative controversy of appointment, there are notable differences -- Wood looking like the most likely to spark a fight, Garland the least likely, and Kagan somewhere in the middle. Kagan would be a change in being a rare (in recent times) Justice with no prior judicial experience -- folks vary as to whether that's a good or bad thing. At the same time, she has a reputation for being a consensus-builder -- an attribute Stevens shared and that Obama may thus value in the ever-present battle to secure Justice Kennedy's vote. Kagan also is probably the most sympathetic to expansive executive power of the three.
Garland is known for being a "moderate", although I'm not quite sure where that reputation comes from -- I had always thought of him as the second of the two liberal lions on the DC Circuit (alongside Tatel). And Wood, for her part, might be the purest intellect of the threesome (no knock on the other two) -- if Obama wants someone capable of going toe-to-toe with Scalia, Wood is battle-tested from her years of sparring with Posner and Easterbrook on the 7th Circuit.
Of course, the three do all share one critical attribute: all are clearly qualified and would make stellar Supreme Court Justices.