I dunno, with Batman I like the "no-killing" thing because, well, he's still a human being and he has to live with the things he does. He also likely wants to stay as much inside the "law" as he can and killing someone will be crossing that line too much for him. It also creates interesting situations like when he saved a mortally wounded Joker because he didn't want to be responsible for his death, or when Batman realized it was time to retire when he reached for a gun to save himself.
One of the bigger reasons Batman doesn't kill is that he doesn't want anyone to suffer what he did when lost his parents. Sure, this doesn't apply as much with his big villains but, still, it's an interesting aspect to him.
If Batman couldn't
save Ra because he was pinned or something that's one thing. But for Batman to say, "Yeah, I'm not going to save you." is a whole other thing.