#4's provide more weight & therefore more knockdown power, however, less pellets which means tighter pattern really necessary. Many use the #5 size shot thinking it a good compromise of both pellet count AND knockdown power. I use #6 because of the pellet count. It hasn't the knock down pop of #4 but i shoot under 35yds, so im more concerned with simply swarming his noggin. To each thier own.