I have had both the onza carbon bars and currently have the zoos.
The zoos feel far better to me, they are an inch wider than before and my front wheel control has instantly improved its amazing!
They just feel nicer and more trialsy, I don't know about strength because I never had a problem with the onzas but from what I hear the zoos are better.
Main point to finish, the zoos are cheaper!!!
Cheers