I'm kind of struggling with the concept of character death in my plot right now...so here's how far I've gotten in my own thought process:
*presumably if you're using death as a “plot device”, such as to show the ruthlessness of the evil guy, or to make the hero do deeds he would otherwise not do, it is better to kill off an important side character (aka Dumbledore) rather than a main character (aka Ron). I know some of the people who have commented above have talked about the possiblity of alienating readers by killing off a loved character, but I can't really think of anyone who went, okay, that's it, no more Harry Potter for me, Dumbledore's dead.
*this is really unprofessional, but I'm torn by the thought of killing my characters *wail*
*but yet it feels like in a huge huge war that takes out half the world, SOME of the characters should at least be maimed. I mean, no matter how good they are, you can't be alert and lucky and all that FOREVER. Of course, there is plenty of internal strife to be found, but death does give more ”shock” when making the point