Smart grabs fewer rebounds... and against players significantly shorter, on average. That’s a start for you.... I’ll allow you to build the rest of the case.
Smart is almost always guarding guys on the perimeter and the best players who shoot a lot. If he was standing on the perimeter doing nothing, he would probably grab more rebounds. The difference is marginal anyways. Exact same rebounds/36 for their careers.
More importantly Smart is significantly better at rotating behind the ball, defending bigs, and defending larger wings.
The offense is the question, not the defense. Marcus Smart plays wayyyy bigger than Bogey.