Nice to see that we're promoting acts of fatal retribution. Guess that's the way he was thinking when he offed his victims. Thus, morally, there's little difference
Well first of all they have to keep them alive while appeals go on. That can take a long time since someone sentenced to death is going to attempt to appeal in every way the legal system allows.
Then they have to arrange the actual execution which afaict has a lot of beuracracy involved.