Left hand is the finesse hand, right is the power. I write left-handed, and do most sports right-handed. I can play much more intricate parts on bass lines on piano than treble lines with my right hand. It goes both ways though because when I had an intense shoulder surgery I had to step up the right hand for things like writing and eating. (Try eating cereal with the wrong hand, it's good for a couple chuckles!) And I recently watched GATTACA again and must say when the doctor says, "right-handed men don't hold it with their left" during the pee test scene...he's lying or I'm an anamoly.