Well, for sheer knock down power, the .715 is going to be boss.
Taylor Knock Out Value is determined by multiplying the diameter x weight x speed and dividing that by 7000.
A .54 rifle at 1,800 fps develops a TKO of 30.66
(.530x225x1800) / 7000
A .715 at 555 grains at only 900 fps = 51.02
Them big round balls really thump when they hit.