I can speak from experience but thats it. I have been hit in soft places by .177", 7/32", and 1/4" rounds. Even with the 1/4" projectile being shot at what is the lowest velocity to the best of my knowledge, it still hurt the most without a doubt. That tells me it has more energy. That is just an observation though and in no way scientific.
Then again all that rambling is like a car guy talking about a "butt dynomometer". Feeling a change in horsepower through the set of his pants, haha!
edit: After some math and some googling. A carbon steel sphere 0.25" in diameter should weigh 1.043g. At a velocity of 50 meters per second or about 164 feet per second that projectile will have an energy of 1.3035+- joules. If the velocity is lowered to 143fps or a tick under 44 meters/ sec the energy should be right at 0.99 joules.
Mike Butts
Lets hear it for google and online calculators!