vs.
So the question here is simply: +1 combat checks vs. magicl. I personally would choose the .45 automatic as it's a strong enough weapon even if it's your only weapon. The knife, however, is a better weapon if you have a one handed physical weapon or a two handed physical weapon. But considering you don't know what you have, I'd go with the automatic. What about you?
p.s. I've noticed that after over 40 great debates coming up with new ideas is pretty hard...