I think Westbrook is a more valuable overall player than Rondo but I don't think a team goes far with Westbrook as their best player anymore than a team would with Rondo as their best player. So for that reason, I don't think I would try too hard to trade for Westbrook.
In terms of the off topic debate about how recovered or rusty Rondo is now, he should not be on the court if he is not healthy. If he is healthy, there is no reason for him to not be "in shape" by now.
So I am assuming that we have a healthy and in shape player who is not sharp, working on timing, getting used to new players and a new coach/system. It is kind of like when a player gets traded, that player needs time to figure things out.
With Rondo though, he has been with the team every day including preseason. He should be pretty well schooled on the system and the other players from watching. Playing is different than watching of course but it should not be that tough for a player as smart as Rondo to get past the learning the players/system aspect in this situation.
So now we have a healthy player, who should be in shape, and should know the players and systems just fine. All that leaves is the "rust" (timing, touch, rhythm, etc.).
I would have expected to see more from Rondo at this point so I fear he may not be "healthy" or in shape or full strength (whatever you call it). If that is the case, I criticize the Celtics for having him on the court. Even in a tank year, I don't see why you would do that. If he is healthy/full strength and what we are seeing is due to other factors (rust, lesser supporting cast, limitations that were always there, etc) that could be even worse.