the jugular vein is always the best route becasue it holds the most blood which in turn can feed the vamp for a while. Also, it casues hormones which make the victim feel less victimised. and it also looks lik they r a couple clearly ingaged in some passionate embrace rather then a deaths breathtaking bite. And normally the victim could be found afterward with blood puring out of their jugular. But at most times the vampire does not allow its victim to have alot of blood left. That is why they have to be carefull.