I'm going with cancer here.
I honestly prefer both but thats not what the poll is about. I choose cancer because I've seen the effects it has on people, who I would say doesn't deserve it, but you can't do anything about it. That's not the case with HIV. Like it has been said before in here, HIV is preventable unless by a random circumstance. A friend of a friend of mine is in the hospital right now, cuz he was stupid and had unsafe sex and contracted HIV. I feel sorry for him and then I also don't because there's no reason nowadays for unsafe sex with random people. However, even though he's in the hospital, friends who know his status go ahead and have unsafe sex as well, thinking it won't happen to them, and this may sound very evil of me, but presenting them with a cure for it just seems like an easy way out and a reason to have unsafe sex more than usual.
And I know someone would bring up the cigarette thing as a response for cancer, but liek other people have said in here, smoking is not the only thing that causes cancer. I think cigarette smokers are dumb as well, especially when they know what cigs will do to them.