What's Worse? Atomic Bomb Or Nuclear Warhead?

It depends which you mean. An atomic bomb is often characterised as a single fission bomb (atomic generally referring to a fission bomb and hydrogen to bomb working on the principle of fusion), whereas nuclear warheads often have many separate bombs contained in the same housing.

This enabled one warhead to cover a large area with several atomic bombs, but also enables the warhead to mix dummy bombs into the mix to confuse enemy tracking.