I'm American and my answer is based on the system we have here.
For the worst crimes, life without parole is better, for many reasons. I’m against the death penalty not because of sympathy for criminals but because it doesn’t reduce crime, prolongs the anguish of families of murder victims, costs a whole lot more than life in prison, and, worst of all, risks executions of innocent people.
The worst thing about it. Errors:
The system can make tragic mistakes. In 2004, the state of Texas executed Cameron Todd Willingham for setting the fire that killed his children- on the basis of what we now know was flawed arson science. We’ll never know for sure how many people have been executed for crimes they didn’t commit. As of now, 139 wrongly convicted people on death row have been exonerated. DNA is rarely available in homicides, often irrelevant (as in Willingham’s case) and can’t guarantee we won’t execute innocent people. Capital juries are dominated by people who favor the death penalty and are more likely to vote to convict.
Keeping killers off the streets for good:
Life without parole, on the books in most states, also prevents reoffending. It means what it says, and spending the rest of your life locked up, knowing you’ll never be free, is no picnic. Two big advantages:
-an innocent person serving life can be released from prison
-life without parole costs less than the death penalty
Costs, a surprise to many people:
Study after study has found that the death penalty is much more expensive than life in prison. Since the stakes are so high, the process is far more complex than for any other kind of criminal case. The largest costs come at the pre-trial and trial stages. These apply whether or not the defendant is convicted, let alone sentenced to death.
Crime reduction (deterrence):
The death penalty doesn't keep us safer. Homicide rates for states that use the death penalty are consistently higher than for those that don’t. The most recent FBI data confirms this. For people without a conscience, fear of being caught is the best deterrent.
Who gets it:
The death penalty isn't reserved for the worst crimes, but for defendants with the worst lawyers. It doesn't apply to people with money. Practically everyone sentenced to death had to rely on an overworked public defender. How many people with money have been executed??
Victims:
People assume that families of murder victims want the death penalty imposed. It isn't necessarily so. Some are against it on moral grounds. But even families who have supported it in principle have testified to the protracted and unavoidable damage that the death penalty process does to families like theirs and that life without parole is an appropriate alternative.
It comes down to whether we should keep the death penalty for retribution or revenge in spite of its flaws and in spite of the huge toll it exacts on society.