I don't think there's an objective way to measure the worth of a life, but for me, length plays a factor. It would feel shitty to save my cat over a small child, because that child has over ten times the amount of time left as my cat and I'd feel like I was robbing them of more experiences than I would be robbing my cat of.
Fortunately, both the men I consider my enemies are older and not in great health π