#1 - and it's not even close.
You don't just look at the blocks or rebounds. Rudy changes shots. He makes guards pull the ball down or not even drive inside. Teams have to adjust what they do. And Rudy can even defend guards on switches. He's made a few look silly (that Andre Miller shot off the side of the backboard should be in his permanent highlight "reel"). Only 5's that give him problems are guys like Gasol and Cousins who have FT-line jumpers and the ability to drive off fakes.
And just think how good he's going to be once he gets beyond the very Rudy-mentary (see what I did there?) offense he has right now. A hook and a jumper from 12-15 ft just to keep defenses honest. That's all he needs.