While I've never been victim to either crime, I have witnessed both. I've also met some of the most vile, despicable scum you could imagine.
In my opinion rape is the greater of the two evils. As many have pointed out, murder can be justified under certain circumstances. There are people out there who are to powerful and too dangerous to be left unmurdered, even in prison. I've met them. I have no compunction about murdering such people. I've never met or heard of anyone who is too dangerous to be left unraped. Some might argue that murdering murderers is wrong. I would argue that if a man strangles a 10 year old girl on a whim, that he has forfeit his life.
As far as my rankings of crimes go, my top three are:
1. Torture. (Nothing that Hollywood can make or that you can imagine comes even close to the toll it takes on the psyche. Unfortunately the ticking bomb scenario does sometimes justify it.)
2. Rape. (While I believe that rape is never justified, when I compare it to torture it just comes off as very, very, slightly less evil than torture.)
3. Murder. (Can be justified, often quite easily. Murdering murderers, self-defense, etc. There are often clear and tangible motives behind murders, even petty ones like money.)
To be honest I'm not entirely sure that rape and torture shouldn't be tied for first place; as one post pointed out, rape can be considered torture. But then, many torture victims are killed after the necessary information is obtained, whereas most rape victims are left alive, so it's debatable.