I don't think it matters for skinning. I use a tripe knife for a quick run up the inside of each front leg and anything I've got to hand to free off a bit of stubborn skin/membrane here and there, but the majority is done by hand not knife. Where you are freeing the skin from the meat I think there is a disadvantage in overly sharp - you want to be able to rub the blade over the skin so it frees off the attached membrane rather than cutting through the skin.