It's a difference, yes, but the principle is that you've taken something from the person that can never be returned.
The fact that the government is sometimes inept and that justice is flawed doesn't change two things:
First, that punishing criminals for their crimes is rightly a role of the government, and second, that there are some crimes that are so heinous as to merit a death sentence. Dylann Roof for example.
Or Joshua Komisarjevsky, who recently had his death sentence reduced to a life sentence. This is a man who, with his accomplice, invaded the home of a doctor, robbed them, raped and murdered his wife and 11 year old daughter, then set the place on fire with the two daughters tied to their beds doused in gasoline.
And recording the raping of the wife on his cell phone.
That this man is permitted to remain alive is not an affirmation of life but a cheapening of the seriousness of murder, and a horrible slap in the face to the victims.