Actually, I guess that on a narrow person-affecting view, the first outcome would not be worse than the second, because plausibly a pandemic of this kind would affect the identities of subsequent generations. Assuming the lives of the people who died were still worth living, while the first virus would be worse for people—because it would kill ten billion more of them—it would not, for the most part, be worse for particular people. But that seems like the wrong kind of reason to conclude that A is better than B.
Actually, I guess that on a narrow person-affecting view, the first outcome would not be worse than the second, because plausibly a pandemic of this kind would affect the identities of subsequent generations. Assuming the lives of the people who died were still worth living, while the first virus would be worse for people—because it would kill ten billion more of them—it would not, for the most part, be worse for particular people. But that seems like the wrong kind of reason to conclude that A is better than B.