Very good framework for looking at the problem. My answer is still non-sentient-vat-people, assuming it can be done cost effectively in a relatively small area. A few humans are presumably sacrificed during the research necessary to breed the vat-people, afterwards it doesn't affect sentients.

The extinction of humanity is a separate issue, which will happen regardless of whether we're eaten, because the vampires want our land. (We are similarly doing the same thing to plenty of animals that we don't eat). My preference is for the vampires to do their best to live in concentrated areas to avoid driving us to extinction. My actual expectation is for the Vampires to, at best, create large reserves a la National Parks where we live mostly on our own.