It’s neither. This would assume there are consequences to either action. There aren’t. From either perspective. Some Christians and people of other faiths will try to tell you that not believing in their God in their way will cause very not-nice things to happen to you when you die, but nothing about any of those beliefs is in any way consistent.
The Catholic Church has the conception of sin. A reading of the Wikipedia page on eternal sin is useful.
God’s capacity to forgive is unlimited, He will grant mercy to any who wants it. Therefore, an eternal sin is one which can’t be given because the person does not want it. It’s like a jail cell where the door isn’t locked. Are you really being jailed?
With the way the world is nowadays, you can simply live your life and settle with God after you die. He’ll forgive you, if you want him to.