Some of it also is the ports preference, based on the ship, the port conditions etc. I forget the show off the top of my head but the camera crew followed the one of the Oasis class ships thru her first Carribean sailing One of the ports they came into, the port at the last minute decided last minute changed the pier assignment, but the ship was already committed to the original pier, and another port, they made the ship turn and back into a slip even though the Capt was going to nose in. The reason ended up being that the tidal current would have had more of an impact when the ship left so they had them turn before docking so there wasnt an issue later.