Well, when I think about this, I guess I think a dull, jagged, or even a serrated blade is going to do worse surface damage, and create an uglier wound that is harder to repair. But I wouldn't think that it would be better for self defense. I mean I don't think Michael Janich designs a self defense knife for Spyderco, and then says "Ok now make it a dull jagged blade." A scary sharp knife is going to cut deeper, with less effort, which means potentially severing more muscle, tendons, and certainly more veins, arteries, and capillaries in a well placed slash. I would think it would lead to more profuse bleeding, and perhaps more debilitating wounds than a dull or jagged blade would produce.
If that's incorrect thinking, please correct me. Like I said, I'm not an expert by any stretch of the imagination.
I thought this referred to the safety of the knife user, in that a sharp blade will cut with less effort, and therefore there is less possibility of the user applying too much force and slipping with the blade, and cutting themselves.
Again, If I have this backwards or incorrect, please, someone with more knowledge correct me.