And on BOTH alternatives, you'll have a nuclear winter than will vanish humankind from the Earth - which is a good thing, if you think about it.

Whoa! So you're saying that TWO bombs will wipe out the human race? We've set off what could collectively be compared to that in the past (especially considering North Korea doesn't have the "Big Boomers" yet; oh God, I just quoted Jar Jar in a conversation about politics! The end IS near!). Nuclear weapons are damn dangerous, but they're not frickin' asteroids.