Why either one of options? Why not to do that at the same time?

Just take resources from military spendings and put them on both tasks. But right, humans need to learn first how to trust each other...

As one wise gentlemen in Russia once said "большая беда нужна" / "we need a big trouble" for all of us to work on such global task. Is this the only option for creating humanity deserving motivations? Not a star but [relatively] small asteroid on crash course with Earth, are we ready?