I don't agree with RBG's theory of constitutional interpretation, but at least she has a recognizable one and employs it. You can actually have a discussion with RBG because, when she writes, she makes her points clearly and within a consistent framework.
As I see it, Sotomayor is just all over the place. The only consistent thing about her framework is that the side she favors should win. Sotomayor because famous when, as a District Judge, she ended the 1994-95 baseball strike. Of course, she threw out the law to do so. She just sided with the players and ordered the owners to open their spring camps in 1995. I couldn't find any definable legal principle that allowed her to do what she did, other than it was the result she (and other baseball fans) wanted. "Play ball!" As Roberts has said, the job of a Supreme Court justice is to be an umpire.