Oberto was a horrible defender in the regular season. So horrible in fact that it's pretty likely that Elson was the better defender. In the playoffs, Oberto picked it up and was worlds better defensively than Elson.
Nevertheless the Oberto stats of playoffs wasn't good either. And Oberto was better defender than Elson in the playoffs. He did a great job playing D against Amare, Boozer and Z. How is explained that?.

I think that the stats aren´t everything.