So lets say you can draw and shoot with good speed and have shot placement where you can land multiple shots right over the center of the heart in an area that has the diameter of one inch so that your shots would just about be landing on top of each other. Now, lets say you could be a little faster and land your shots in the same spot, over the heart, but now your shots are wider so that they cover an area that has a diameter of three inches. You are still hitting the heart and lungs but by speeding up a bit you sacrifice some of the pinpoint precision that allows you to land your shots all within a one inch diameter. As for me, I would rather be a little bit faster and still be able to hit the vitals. That way even if the bad guy is a bit more accurate than me I will shoot him first and I will hit him in a spot that will hopefully stop him before he is able to get off any shots at me.