Depending on where the batter stands in the box, the difference in distance to first base is about 2 feet, or for a reasonably fast runner, about 0.07 to 0.08 seconds. The remainder of the 0.2 seconds is presumably caused by the rotational direction of the left handed batter's swing, which tends to point him toward first. A right handed batter tends to end up facing towards third, so he needs time to turn back toward first base.