I just think CP3's steal numbers tend to inflate how people judge his defensive ability.
So do Rondo's. But in both cases it's not like steals just fall in their laps either. In today's game (with the rules and the talent) there really aren't any defensive stalwarts at PGs. Just guys that are better than other guys at the position. CP3 is a very good defensive PG who struggles with bigger assignments who can body him. Considering the position, he doesn't have to worry about that all that often. Defensively, Rondo is the only PG I'd put in a discussion with him (atm... the youngins could knock him down a bit soon, including Westbrook).