I would have rather they killed off Samantha Wildman, as she was the recurring character whose death would have had the most impact for the maximum number of characters. It would have affected Noami, Neelix, Seven, Janeway and the audience. We were much more emotionally invested in her than in Carey, who we had only seen once since Season One. To be honest, when I first saw the episode, I didn't even remember who Carey was. I honestly thought he was another redshirt.
The same holds true here in Battle Lines
. If they had allowed Opaka to be in two or three more episodes (hell, just one more would have been beneficial) it would have meant more for the audience, which is what they seemed to be going for.