It's no coincidence that Bruce Bowen's five most formidable years in the NBA were marked by 3 Spurs les. Bruce owned the court from a defensive standpoint and put fear in the opponents he was guarding. San Antonio had the hard edge you need to win playoff games with him on the roster. He was every bit as important as the Big 3 during those le runs. When you average 6 points a game on offense, but other teams still have to game plan against you, you know your defense is something special. Bruce probably could have scored a lot more points on another team, but he knew his role and carved out a great career as a defensive specialist.
I love Leonard's ceiling. He's become one of my favorite Spurs. I think he can be everything Bruce was and more. Unfortunately he's got superstar teammates who are 8 years older than the versions that Bruce got to be on the court with, so we may never really be able to compare the two. Bruce was never asked to be much of an offensive player, and he didn't need to be with Manu, Duncan and Parker all in their primes. He could concentrate completely on D, and as long as that corner three was falling through the hoop 40% of the time all was golden. Leonard doesn't have that luxury. He's going to have to carry much more of the overall burden than Bowen ever had to during his Spur career.
Green is more of a situational player at this point I think. He's not particularly great on defense, although he surprised me at times in the playoffs. He's not a great finisher. He's not a rebounder. But, like Leonard, he has a lot of room to improve certain parts of his game. We'll see.
In a hypothetical world, if I owned a team and had 2008 Bowen I'd trade him for the current Leonard+Green in a second. 2005 Bowen I'd have to think about, but I'd very likely do that trade as well.