I prefer the brain overcoming the brawn. The victim, usually a baddie, is often bigger, stronger, better armed or a member of a bigger group. He or she gets their comeuppaance from someone who is quicker, smarter, more determined. For this, a normal human, most of the times female, is best.
But I also do like monster horror movies, where groups of (not necessarily evil) people get decimated in gruesome and/or funny ways. In this case however, I don't like the situation to be objectively hopeless. People fighting and dying heroically against an almost invincible alien or hundreds of zombies does nothing for me. I love to see them fall victim to their own ignorance, overconfidence or greed. The monster is just a tool.
An insane killer, even though technically a human, is often more like the "tool monster" than like the normal human who gives baddies their comeuppance.