What can be said for sure is that in the past few seasons Westbrook has been a part of some of the most offensively potent 5 man units in the league. Rondo has not.
Sounds pretty definitive. I mean players like Fisher, Sefalosha, Perk and Collison have been part of great offenses when players like Kyrie Irving, Mike Conley, Marc Gasol and Greg Monroe haven't.
The point is that it's
not very definitive. But there's very little in the way of convincing proof that Rondo is such a boon for an offense, while Westbrook is such a detriment to one.
I can look at the big picture results, though, and say that if these assertions about Rondo being so much better for an offense are true, we haven't seen him actually lead a prolific -- or even very effective -- offense for an extended period of time.
What I know -- for whatever it's worth -- is that Westbrook has been a key part of a deadly offensive machine for the past few years, while Rondo's team has regularly been a below average if not outright bad offensive team for much of his career.
At his best, Steve Nash was at the helm of some of the most potent offensive squads in the history of the league. I think many of the positive things that have been said in this thread about the impact of having a great passer probably applied to Steve Nash. Steve Nash seemed to improve the shooting of his teammates every time he stepped onto the court. I'm not discounting the idea that a great passer can be the focal point of a deadly offense.
There is evidence -- much of which has been recounted in this thread -- that Rondo has had a positive impact on the scoring efficiency of his teammates. However, Rondo has yet to be the focal point of a strong offensive team.
The theory that Rondo could elevate a team of lesser talents (or a team like OKC with one or two greater talents and a lot of lesser ones) via his passing alone makes some sense -- but the bottom line is that as of right now it's nothing more than a theory.