Bear in mind that when it comes to morals, better and worse are points of veiw. Don't be afraid to speak your mind, there is no way to answer this question correctly or incorrectly; it's opinion in its purest form.
I'd say rape is worse; after you're murdered, you don't have to suffer through emotional trauma because of it. It seems to me that, while neither are legitimate, murder is done to solve a problem while rape is done to cause pain, physically, mentally, and emotionally, and it does not solve any problems.
Suppose a guy's wife cheats on him. He takes a 38 special and puts a bullet in his wife's head, then he puts a bullet in her boyfriend's head. Let's analyze that.
There were countless better ways to solve that problem. I think he was wrong in doing that, and I wouldn't have done it if I were him; but I could understand why he did it.
Now suppose instead, he waits outside for the boyfriend to leave, then goes in and rapes his wife. That I could not understand; that didn't solve any problems, and he hurt his wife a thousand times worse than one bullet to the head ever could.