Neither. I hunt them.
But I'll play along for now. I prefer vampires simply because Molag Bal created them, and Molag Bal rules! Molag Bal > Hircine :meh:
(Wow I said Molag Bal 3 times in one sentance
)
Molag Bal is not the confirmed creator of Vampires. Vaermina seems to have a pretty big hand in things too. All infected have nightmares prior to the full transformation. Molag Bal has to get the cure from her(Why would this be necessary if he made them?). Vampires are often referred to as nightmarish. They're tied to the night, which is related to sleep and by extension dreams, also Vaermina's forte. I could see that story about Bal and Lyrae being either true or false though, so I'm not certain either way.
I'd like to see some situations as described by On Lycanthropy to be present in TESV though. People sitting in a bar, a beggar sitting over in a corner suddenly transforms and kills a couple patrons. Everyone(save a few foolhardy would-be heroes) rushes out and the owner locks the door behind them until the guards and a professional can deal with the situation.
I'd like both to be in TES5, especially if it's Skyrim. Vampire clans have some seriously unique abilities. Having several werecreatures would be neat too.
I like to slaughter them both though.