what qualities of the two works help create this distinction?
They both are pretty far fetched. Becoming one's darker half and altering ones DNA to be younger again are the stuff of science-fiction. Still if I had to pick one, I suppose being young again might be, in 200 years, sort of possible or at least some sort of variation of it. I think from a sociological point of view the results of Dr.Heidegger's Experiment is quite plausible even if the experiment itself is not. Humans make the same mistakes over and over again throughout history. It matters little that we see the results of these mistakes, we make them again anyway.
