As a cruiser that has done a high number of cruises, the long and short of it is mid ship for stability issues. If you get seas sick or think you may, see a dr for the scopolamine patches. Otherwise think of it as the front and back (the latter for sure), will give you the most rocking lmotion it that’s an issue.
I also plan by ports and the direction of the ship whether I pic port or starboard. Sometime you luck out and see land to either side depending on direction ship is going, so I always check the map.