Even a plain edge is not smooth when looked at under a microscope, it is actually a multitude of small, microcopic serrations like a saw. Thus, the smaller the serration, the cleaner the cut. No matter how sharp a blade with visible serrations the size that are available in today's broadheads, they will not cleanly cut due to the angle at which each serration cuts at. That trauma is what creates the tearing and subsequent hemostasis through vessel constriction. I'm not saying it won't kill game, all I am saying is that bleeding is better with a cleaner cut. Some other things to also be concerned with on serrated blades are the increased chances of infection and future mortallity on poorly hit game with relation to hits that would otherwise heal. Serrated blades create wounds that are gapping and normally require suturing to close, thus allowing more chance for bacteria to invade. The other is decreased penetration due to each serration "clogging". Serrated blades, such as those on knives, have to move back and forth like a saw in order to "clean" themselves out for each impending cut. As far as I know, a properly placed broadhead is intended to move only forward.