So the thing is, normally I'd say c'mon, with how modern vampires are so often described, the advantages WAY outweigh any disadvantages--you got the eternal life, the magic powers, the super strength, asking to go vamp is a no-brainer!
But in this case it might be it really IS a no-brainer--does turning into a vampire make you an idiot like they all are? That'd be a serious drawback.