Car wheels spin at different speeds, especially when turning. The wheel on the inside of a turn has to travel a shorter distance than the wheel on the outside of the turn. This causes the inside wheel to turn slower than the outside. On non-driven wheels this isn't a problem, but on the drive wheels this could have adverse characteristics if your goal is speed and handling.
Replacing the diff with an LSD will reduce this tendency and put more power to the non-slipping wheel and less is wasted on spinning the other tire. This will allow for better acceleration out of corners.