DEAD!!!!!!!!!!!!!!!!!!!!!!!!
you could search the forums for hours and find many posts on this.
it all boils down to dead is safer, less stress, and less of a hasstle. i can get 10 dead rats and that lasts a month in the freezer for both snakes. the only benefit i know of frozen food is there are slightly less nutrients due to the freezing and thawing. but you can always feed a fresh killed mouse every other few feeds to get the snake everything it needs. the only people i know that feed live are newbie owners (like i was once myself).