[mabbo]

More problems that are smaller may be better overall. With more total surface area, the air would absorb more of the total energy coming at us.

You don't want another K-T extinction event when you could just have three cities wiped out instead.

[workitout]

If you can guarantee just three cities. Either way, not sure why I was downvoted for having an opinion on the matter. Also I'm wondering why HN moderators allow such downvoting which discourages well intended discussion and participation.