I think as a general rule, lefties are more aware of their surroundings. Because most stages are right-hand, a left-handed person has trained themselves to be aware of the muzzle direction in all situations.
Not to put down right-handers , but I feel that they do not think about the direction of their muzzle after their first couple of matches because the majority of stages are run left to right. During this time, they see that the muzzle automatically points downrange in a safe direction and don't ever think about it again.
<on soap box>
My personal peeve is when a R.O. cautions everyone to be aware of their muzzle because the stage requires the competitor to move to the left down a wall parallel to the 180°, but not for moving to the right. Does the R.O. do this because he/she thinks that the competitors are dim or because they haven't been trained to be aware of the muzzle direction so they have to remind everyone? Why don't they warn the lefties when the stage requires the same movement to the right.
<off soap box>
Because most stages are right-hand friendly, I have trained myself to shoot either way with equal ease. I weigh all of the factors, and then attack the stage in the way I think will yield the best score, whether it is the right-handed way or left-handed.
A group of physiologists wrote a report years ago that left-handers are more adept at handling challenges and crisis because we face additional challenges everyday living in a righthanded world. Clocks, cars, micrometers, hand shakes, etc.
To answer your question, I think that lefties are better when moving against the grain.
Kenny