Christiano strikes me as the sort of person who would embrace the Repugnant Conclusion; whereas I think Yudkowsky would ultimately dodge any bullet that required him to give up turning the universe into an interesting sci-fi world whose inhabitants did things like write fanfiction stories.

Nobody actually acts like they believe in total utilitarianism, but Christiano comes as close as anyone I know of to at least threatening to act as if they believe in it. Yudkowsky, having written about complexity of value, doesn't give me the same worry.