A couple days ago we booked a cruise on the Norwegian GEM. NCL had a great kid's sail free promotion going on, BTW. We picked and inside stateroom and it was of the status GUAR (Guaranteed IX). That meant the cabin was to be assigned later.
Today I logged into NCL.com and found that our cabin was assigned. It was category ID. The worst inside category was IZ, while the highest upgrade you can get inside was to a I1. But I wasn't sure what the differences were. Despite all the differences, they were all 143 square feet in size.
Apparently, an I1 is a Family Inside room which could possibly enable a 5th passenger in the same cabin. IA to ID are on higher decks, which are supposedly better, with IA and IB's being more in the middle of the ship, and thus improved convenience.
Then you have categories of IE, IF, IX, IZ which are on the lower decks- usually on deck 4 or 5. Being lower down you would have to climb more stairs/stay longer in elevators.
