Rondo has a much bigger defensive edge over Irving then Irvind's offensive edge over Rondo IF healthy. If you look at the NBA's new Player Impact Estimate, then Rondo, prior to his injury, had slightly better stats. PIE like PER is biased toward high usage shooters and to offense over defense. Even with both these biases in his favor, Irving trails Rondo.
Stepping back, neither are elite offensively like LBJ and KD though they are both above average. Irving is better overall offensively than Rondo but the edge on playmaking goes to Rondo. OTOH, Rondo's edge defensively over Irving is huge IF healthy. Rondo has been an elite defensive player by the numbers pre-injury. Irving is below average for his career and last season.