We know that both Hugo and miles can talk to the dead. Miles "senses" them, and hugo sees them in person.
The thing i noticed was that miles has all the time in the world to talk to the dead. Hugo can't, the dead he talks to vanish after saying what they want.
Also, Hugo talks to "ghosts" and miles needs the corpes to talk to.
Although the two have the same "ability" I reckon that their subtle differences will hugley impact the story.