To break it down further look at this year. There is a common theme about most playoff teams still playing. It's the front Court.
Boston - Ridiculous amount of former allstars/superstars in the front court.
Bulls - Booze/Noah
Lakers - Gasol, Odom, Bynum
Griz - Z-Bo, Gas
OKC - Ibaka, and perkins for D, Collision as their Jared Jeffries
Miami - exception due to Lebron
ATL - Josh Smith, Jason Collins to play Defense
Dallas - They have size for defense in T Chandler, and Dirk Is Dirk. good backup in Haywood.
Size means better defense. Come the playoffs when they allow more contact so it only helps your team to be bigger. In all of these they have one good/great offensive Big Man paired with defensive Bigs. Either a tandem of defensive bigs or one guy who can get stops. Not ronny turiaf who as much as i like his game is just undersized.