In the real world I think the differences are often so subtle that it does not really matter to the extent of overcoming solid hitting and possibly some superior 1B skills at fielding less than perfect throws.
From a technical standpoint, a lefty has a slightly better setup when holding the runner (righty has to cross his body with his left arm to get glove in position to tag) and the lefty has a better setup when throwing down to 2B if they receive a throw from the pitcher after the runner has left (can throw the ball on the "inside" whereas righty may need to step to his right so he has a clear throw to the outside). Again minor, but helps with fielding when holding a runner on 1B - you get a little extra range on the glove side and so getting back into fielding position is generally 1-2 fewer steps). If you have two guys that hit identical and basically field identical (very seldom happens) then the lefty might have a small advantage - think of it like a tie breaker if needed.