Is it, perhaps, that Clark's death, unlike Lois's death, would be too big a loss to be cathartic?
Personally, I would find it easier to kill off Lois for the simple reason that she *doesn't* have superpowers. It has nothing to do with the fact that she's female. It has everything to do with the fact that she has no superpowers. It takes a lot more "work" to kill off Clark. I've been toying with a fic that does just that for over a year now and it's darn hard to kill the guy.
