The biggest difference is that shots are actually being contested from mid range. Last season the Spurs' defensive game plan was to avoid giving up 3's and shots at the rim, but they basically conceded mid range jumpers, which as we all know came back to haunt them against OKC in the playoffs. In the first two games of the season the Spurs are actually contesting shots from mid range, but still disrupting forays to the hoop and 3 point shots as well.
A big reason for this seems to be the limited minutes of Bonner, Blair, and Neal so far this season. Our lineups are quicker, and as a result guys are rotating well and contesting shots. Can't ask for much more, tbh.