I knew that was the case with some guns, but I didn't know it was with every gun. (Damn Wikipedia)
Anyway, what I heard was that with the lower rpm gun, the hits per 100 (I think) shots was about 12 on a man-sized target, but with the higher rpm gun you get about 76/100 hits, because the firing action is so fast, it's more like a vibration instead of jumping all over the damn place. At least it was something along those lines.
All hailz das Einhander, who actually knows this stuff!