New MacBook pro

You should use Setup Assistant when you first set it up; best way for that is from a backup on an external drive. Migration Assistant can be used later, but it will create another user account since you've already set up yours, so there will be duplicates. The initial Setup Assistant is best.

By the way, Setup Assistant is automatically offered during the setup phase asking you if you want to migrate data, so it is not a separate app and it is only offered once.