Interesting–and colorful–column by Professor Ralph Rossum comparing Sotomayor and Souter. Rossum argues that even though their voting patterns are likely to be similar, the most notable element of Souter as Justice was his inconsequentialness:
There is every reason to believe that Sotomayor will be an equally reliable member of the liberal team. The crucial question, however, is whether the Souter seat she is assuming will remain at the end of the bench.
The question is crucial because, while Souter added “bench strength” for the liberal team, he was seldom assigned to write the majority opinion. Some statistics: Since Souter’s elevation to the bench in 1990 through the end of the last court’s term, the Supreme Court has handed down 1,587 decisions. Souter has written the majority opinion in only 135 of them