Once again, however, you'll be comparing apples and tortillas.
IF Bobby has a productive season as a starter with the Grizzlies, it won't mean he would have been as productive off the bench for the Kings. And, in reverse, if he isn't able to do well, it doesn't mean he wouldn't have done well with the Kings.
If Bonzi doesn't have a productive season with the Kings (something which I do NOT think will happen), you can't compare that to what might have happened on the Grizzlies because there was little chance he would have stayed there. He would almost certainly gone somewhere else.
The idea of judging how someone might have done had they stayed put is interesting, perhaps, but it doesn't really mean anything. It's an exercise in "what if" and that's always purely subjective in nature.
Bobby is gone. Just like Webber is gone. Christie (at least for now) is gone. Vlade is gone. Jon is gone. Jason is gone. Scot is gone. Hedo is gone. Gerald is gone. JJ is gone. Tag is gone. Damon Jones is gone. Mateen Cleaves is ... well, I think you get the idea.