This is going to be tricky answering without someone getting riled. @_@
So basically, I feel murder is *far* worse. For one, I feel that if a rape victim would have vastly preferred death over living through the ordeal, the suicide rate should at least be higher in that area, rather than the 13% there is. [http://www.suicide.org/rape-victims-prone-to-suicide.html] For two, if you can justify taking someone's life, there very sense of freedom, redemption, second chances, the joys that life offers and send them to the unknown (Heaven, Hell, Nothingness, your choice), either out of revenge, "justice", or self-defense, then all you have to do is go out of your comfort zone of morality and apply the same logic to rape. With that said, I'm going to raise my shields now and say that your typical reasons for either of these acts in my books is worthy of a shot to the head, and if you raped someone, suffering before the shot to the head. I just don't think a regular slimeball rapist/killer has the same value of life as a good person does. And for three? Saying there's no reason for rape as a reason it's worse won't work. There's absolutely no reason to spit on someone, either, or to name call. Does that make it worse than murder?
All this said, when you kill someone, there's no coming back to that. There's no long road to recovery and eventual happiness. And in most cases, this happens to the good people of this world. Rape victims for the most part, survive, and many of them, stronger (though it REALLY shouldn't happen to them in the first place. ~_~;; ).
tldr: Murder is worse to me; kill both types of criminals that have flimsy and/or no true justifications for their actions. I hope rapists get raped, murderers murdered, and my opinions stem from a dark yet insightful novel. ~_~