Ok... But this is 'my' canon. And vampires can get horny as fucking hell, succubi can suck out the life force of any gender (even attack helicopters) and vampires can drink any and all blood to sustain themselves. Obviously when I ask this question I meant that they can devour one another. The question is, who'd win?
A Succubus feeds from male sexual energy and vampires are undead so they can't get erections. On the other hand vampires can only feed from human blood so no demonic blood would work.
Vampires being undead do not die from hunger, they just get more feral, so the vampire will survive unless the Succubus somehow kills it.