If you stab someone, the force of how to kill someone plus the fact it's a melee attack means you'll only get enough time to kill one or two people until you're stopped/people runaway. Even then, it's easier for police to stop someone with a knife. A gun on the other hand can allow you to kill multiple people at once... Even with this argument being so thin on 'how many do you prefer dead?' The answer is... As few as possible.