The Mythbusters tackled this old saying. They found (in a random sample) that boys throw faster, while girls are more accurate.
However, one of the more interesting findings to me was that the boys had a more aggressive throwing stance,,,, until they they considered the question of was this stance a learned behavior, or a product of nature? So they turned to a pro softball player, and a pro baseball player, and found that they both had similar throwing postures.
I think this ads to the arguments of which is stronger, nature, or nurture?