What is the advantage of half wave rectifier over full wave rectifier?

The advantage of a full wave rectifier is that it produces less ripple and the ripple has a higher frequency, making it easier to filter.

The advantage of a half wave rectifier is it is simpler and less expensive as it needs fewer components.

Which is best in a given application however requires making other tradeoffs that are out of scope for this question as they cannot be determined without knowing the details of the specific application. So neither is universally the best.