I think the most interesting part would be the authenticity. Ghosts, if they exist in the context of the story, are from a different realm. So their story might not be bound by the normal rules of the living world. They could tell about events that no living person has witnessed, like what really happens in haunted places at midnight or the secrets of long - forgotten tombs. This would give the story a sense of the unknown and draw listeners in with a sense of wonder and a bit of fear.
The most interesting part could be the unique perspective. Ghosts have experiences beyond the living, so they might share insights about the afterlife or hidden histories.