Leonard hands down...
Aside from Butler, who was highly overrated from Bulls fan, as if he was going to shock the world by scoring 20 PPG, and become the next second coming of Jesus.
Butler is your typical above average 3 and D guy. He can shoot the 3, and can defend LBJ pretty well. He definitely did a better job than Leonard, but it came down to length/body size versus quickness/intelligence. Butler is athletically pretty gifted, and has a shorter wingspan, but he did a better job of taking or staying in front of LBJ.
I'd rather have Leonard. He's the all around player. Take him over Batum any day for versatility. He knows how to pass, can rebound really well, and can score in multitudes of ways.
Plus he is like a year younger, and hes already developing so quickly. I can't really imagine Batum guarding LBJ/George.