I'm not even sure his defense is better than dc anymore.
Its not.
Rondo just isn't a good PG anymore. As MassKingsFan said, he's not even close to the defender he was during the prime Boston years and is just an average defender now. And that's when he wants to be. He still can't shoot/score a lick. And he requires a lot of ball dominance to be effective as a passer.
Give me DC and his consistency across the board in pretty much everything over Rondo's huge flaws. Rondo has been living off his name since the 2011-2012 playoffs.