-PJ
I'll answer your knife question.
Knife killings are very personal; you have to be up close to the victim. Gun killings, especially rifle killings, can be from far away, and many times are random (if the killer is crazy enough).
Therefore, the knife killing is the one where the killer is "more likely to find another way" than the gun killer. The gun killer will find another victim; the knife killer will find another weapon.
-PJ