Further details: you should always be moving, the balance is never stable which is why you can't prop a hoop up in the middle of the room by just balancing it. While your adjustments may become very small, you never, ever, stop.
Head balance is easier in my opinion because it's closer to your eyes. It's more like a first-person view. Your neck may become sore. This isn't a problem per se as long as it's soreness and not pain. If it's painful, STOP.