If I was going to buy a gun that would be used only for deer hunting, it would be a rifle (unless, of course, you have a few rifles and are looking for a little variety).
As for your specific question about using a patched ball in that gun, I suspect it would be a bad idea. So far as I know it's designed for turkey hunting and has an extra tight choke. Ideally, you want a cylinder bore or very little choke when shooting balls from a shotgun. Hopefully one of the Knight TK owners on this forum can shed a little more light on this for you.