If Al wasn't so robotic and sad with his post moves and/or a rebounding beast, This wouldn't even be a discussion. But since he is, its absolutely vital for him to be able to take other PFs off the dribble. Even if it's from midrange. Thing is, Al rarely does that, even on centers in which he has a quickness advantage over. If you put him at his "natural position," that advantage no longer exists. For Al being what he is, Millsap gives us that and more on offense. I'm not sure if Al's defensive advantage over Sap would be that great on quicker PFs who would just take him off the dribble. In summation, if you have both at PF, as of now I'd choose Sap. Sure, Al's midrange jumper is a little better but once you take that away what are you left with?