Since torque is defined as "twisting force" the L setting will give you more push/pull capabilities over M or H.
Going up a steep grade with loader full, you will find L setting to be very valuable over the M and H.
Many people with the 3 ranges seem to use the M setting a bit more, the H more for transport and the L when they need more low "gearing" to get into a pile for the FEL.