If OKC were to have Rondo, they would need another scorer to start.
There would be too many "defensive" type players in their starting lineup.
KD would be seeing double, triple teams all the time.
I think Westbrook's offense is good enough to make defenses respect him and keep them honest.
Westbrook just needs to learn how to make better decisions. He's still young and probably the better player at this stage in his career compared to rondo.
This is exactly the point which I think is often missed. The man that doesn't have to cover Rondo causes a lot of problems. There is not a direct stat for this so you can't prove or measure the impact.
Both Westbrook and Rondo are flawed but emerging stars. I think Westbrook feels like he needs to be Robin, the #2 guy on OKC and just like happens with Davis sometimes, he tries to do a little too much on his own. He is the #2 guy though so he can't just pass to Durant every time.
On the Celtics, MAYBE, Westbrook would feel a little less pressure. He certainly would not need to be the #2 guy. That situation may benefit him or maybe he likes being the bigger fish in the smaller pond.
Either way, I don't see even trader Danny making such a lateral trade. It is hard to see the old guys liking Westbrook better than they like Rondo. Even though I think they would get over it if Westbrook played well (which I think he would do) it would not be good if Westbrook came in with an attitude and then pouted with KG barked at him.
Another way to look at this though is in OKC, Westbrook will always be Robin. In Boston, he could be Batman in the future although he would have to be pretty patient.