Let's go extreme:
  Everybody dies except for two situations:

  20 year olds only Earth.
  2 months old only Earth.

  I'd choose the 2 months old only Earth. There'd be more death?
  Likely. Would some survive? Likely. What would come out of it?
  No idea. *That's* what makes it more valuable to me.

  With the 20 years old only Earth, it's pretty predictable what
  would happen. Variations of what we already know.

  Mind you, I wouldn't exist. I would never find out. I'd be dead.
  That's ok. I'd still choose it, were it my last push of a
  button.