Yes, but what does best mean, exactly? "Most capable of critical and independent thought"? What lawyer, whether prosecutor or defense attorney, wants that?
Neither does. Each side picks the jurors it thinks are inclined to be favorable to its position. That's the push and pull of the adversarial system. The theory is that a battle of the extremes will result in a neutral resolution. Of course, the theory can fail if the entire jury pool is predisposed to a certain position.