Both the type of wad, shot and the amount of powder that drives it..no comparison in actual killing power...for the most part the velocity is not that much different but the individual pellets are much harder..copper and some of the new tungston based shot and some others such as Rem.HD and alot of others..they really penetrate and bust everything they touch..also the wad system stays with the load much further out than your standard high brass shell..world's apart for the most part..these are the good ole' days in the turkey shell business..