I think the meat cleavers thing was a deliberate choice on their part. If
just wanted him dead, they could have done it in a much less attention-grabbing way, so it's not about what's an effective tool for killing someone.
Also, like Dan said, proper guns* are designed exclusively to kill things. More to the point, they make it
really really easy to do so – so much so that even killing someone accidentally is very easy.
I would further argue that psychologically, killing someone with a knife is a very different thing to killing someone with a gun. With a knife, you have to get close, in their personal space, and risk retaliation. With a gun there is none of that – the balance of power is overwhelmingly in your favour.
edit:
oops, didn't realise this thread was so long and that most of these points have already been made
:$EDITED: 25 May 2013 07:43 by CAER