Headphones are better if you want to hear every detail of the song as close to perfectly as possible. They're good for recording, and they're also good in settings where you want volume but have to keep others in mind.
Speakers are a better overall experience. You can crank it really loud, so loud your car is shaking, without hurting your ears. You can really feel the power of the music via speakers in a way you just can't with headphones imo.
