Late night hours offer fewer interruptions, the house quiets down, notifications drop off, which creates good ground for deep focus. But the cost of working late carries into the next day, sleep gets shorter, and that builds into cumulative fatigue.
Early morning hours give you a mind that hasn't yet picked up the day's accumulated load, its freshest state. The downside is that not everyone can adjust to those hours easily.
There's no clear winner, it depends on the kind of work and your own chronotype. What matters isn't which one you pick, it's being able to hold that time slot consistently.