I worked in a couple hotels in the past. The rooms booked through any of the online discount travel sites get lowest priority. All of the rooms booked directly through the hotel's website (hilton.com, marriott.com, etc) get assigned with higher priority and get their requests filled first (king vs two double beds, high vs low floor, close to or away from elevator). The reservations booked through third party discount travel sites get assigned last to whatever rooms are left in the system, and if the hotel is overbooked, they'll be the first ones to get walked to another hotel. Edit: that doesn't mean that you'll necessarily get a bad room if you book through a third party site, it just means that if the hotel is fully booked or close to it, you won't necessarily get your first choice of the type of room you booked. If the hotel's only half full, it's not really an issue.