I cannot speak for this ferry, but from experience on other ferries: Deck passage is just that. No assigned seat, sit where you can, maybe an opportunity to get inside for the night. Good and cheap in the "if you don't mind putting your sleeping bag on the floor" type of thing. You do not mention Airline Seats: Many ferries have these, airplane type seat that reclines some, assigned to you, often in an area where they may show bad movies, not a bad option, but like a flight, don't expect to get much sleep. If you want sleep and do not mind possibly being away from your travel partners, the Dorm beds or Couchettes are a good choice, reasonably priced, certainly more comfortable, bit dependent on what you get for bunk mates. A room is certainly the most comfortable and private. Just need to assess whether cost is worth it.