Brig inmates sleep 2200–0600 every day.
Regular sailors work 16–22 hours a day when underway, and there’s no guarantee that there time off will be all at once; in fact, it probably won’t.
Brig inmates get 3 meals a day.
Regular sailors often work through one and sleep through another. Many rely on the ship’s store for food.
In-port, regular sailors may have a chance to leave the ship, especially if in-port 72 hours or more while brig inmates, almost by definition, can’t.
There’s upsides and downsides.