On my recent hunt when I shot a 400 lb Boar one of the property owners hopped right on the boar to start gutting him with his dull S&W fixed blade. Right before he started I said I had a really sharp knife (my Spyderco Mule which was hair whittling sharp) in case he needed one. He started trying to open up the animal and barely got a few inches with some serious force and I told him my blade would make life easier. He grabbed my knife and in shocking speed had the pig opened up with the innards out of the animal without a Nick on him. He could have had a nasty would using his hunting knife, instead he easily got the job done with a very sharp knife in no time and asked me to sharpen his knife like mine. It was the least I could do to sharpen his knife for letting me on his property to get hogzilla, though I said my knife's M4 steel gets sharper than any other I've tried. It didn't stop me from putting a 2000 grit hair whittling edge on his blade ( he does a lot of skinning so I left a bit of tooth) that he is extremely happy with, and no cuts to be found on him.
I have cut my thumb in half lengthwise to the top of my thumbnail being stupid with my Spyderco Native a couple years ago. Lots of pressure from gauze made it stop bleeding by time the ER Doc saw me, and she marveled a cut could be so clean. She was shocked a pocket knife could do that, she said it looked like a giant scalpal did it (after a recent trip the Doctor I found out scalpals are surprisingly dull, my edges are WAY sharper) and she sewed up the meat of my thumb and left the nail alone. The nail never even fell off, and to this day you have to look super close to see the scar from that incident. A dull knife may not have gone all the way through, but at minimum would have made a ragged , ugly cut. I'll go with sharper every time.
Mike