This one is dangerous because you're now establishing that GHOSTS are REAL.
You are changing the paradigm for 99% of human concerns.
1) What is this life about?
2) Is there an afterlife?
3) Is there a heaven?
4) What happens to my soul?
So it's either choose to have supernatural ability or there is the Supernatural.
I would choose the Ghosts, but I'd be concerned on what levels do we talk and what's the disposition of a ghost.
Is it Ghost with Patrick Swayze or 13 Ghosts or, or Silent Hill or ..?
Can they get me the winning lotto numbers?
Can I speak with the murdered and help solve their case and become the world's greatest detective?
Can a ghost help me find missing persons?
Can they impact the world of the living?
Can I raise (no pun intended) an army of them?
Can I speak to the ghosts of famous-dead people?
I'm going with Ghosts, but before I sign the contract, I need to know more details.