20 ga. for Home Defense

Beyond Buckshot - A Look at 20-gauge Rifled Slugs for Self-Defense in the Smoothbore Shotgun

Well worth a read.  One of the reasons I picked up a 20 gauge is knowledge similar to this quote-

When compared to a 12-gauge, the 20-gauge delivers 75% of the lead with a recoil that is 40-50% less.  This is equivalent to the ballistic force of being hit with two .44 Magnum rounds simultaneously.  In addition, the reduced recoil of the 20-gauge is conducive to accurate, rapid shots.