Do I need LifeLock, if I have Dark Web Monitoring?
Dark Web Monitoring just lets you know if your personal information has been found on the dark web. Which would indicate that that information could be sold to scammers. The information found here can be years old, so it is not a real time monitoring feature.
Are you asking about the LifeLock credit monitoring service? This will monitor your protected accounts in real time and also help in the event that someone does steal your identity. Only you can decide if you want/need that kind of protection.