It's a thought experiment. It's like when people are given the question, "Would you kill a crying baby to protect a dozen people from a Nazi patrol," and someone answers, "I'd raise a Zombie army and defeat the Nazis -- don't even have to worry about the baby!" If you don't like the question and its parameters, don't participate.
As for me, the answer is obviously Datsyuk. That doesn't mean that I don't love Z, or that I don't think he's an amazing combination of shutdown forward + goal scorer, which is rare. But his health (back) problems always seem to be one check away from sidelining him for a few weeks, and he seems to be slowing down, despite being younger than Dats. My subjective feeling is that when we're down and need something amazing, Dats is more likely to pull it off than Z.