There's not much to say about these decks! Deck 9 has the second floor of Dazzles. Deck 10 is strictly cabins, deck 11 has a small library and concierge lounge, deck 12 has the second floor of the concierge lounge. Deck 12 also has the largest, and third largest suites. The Royal Suite is 1275sq ft with 335sq ft balcony and the Presidential Family Suite has 1142 sq ft with 476 sq ft balcony. Those two suites are bigger than our first house, LOL!
An inside cabin on the Oasis/Allure ranges from 149sq ft to 260 sq ft (of which, there are FOUR). We had booked "category z" which means you are assigned an inside room, usually in the category Q size (149sq ft), of which there are only 45. Most interior cabins are in the L, M, N group, of 172 sq ft. The first two ships we went on, the interior cabins were 152 sq ft. I can't imagine being in a smaller room, though I guess it's only 1'x3'ft difference (seriously though...where do they take out that space?!). We feel very blessed to have been upgraded to a Superior Ocean View Stateroom with Balcony (182 sq ft with 50 sq ft balcony...the room didn't feel a whole lot bigger than 152 sq ft, and the balcony was a touch small (would have liked a lounger), but still awesome!).
On the next few classes down, the interior rooms are larger--160-165 sq ft, but on the Vision Class they go down to 140 sq ft, and on the Sovereign class they're 119sq ft! Yikes! Some of these smaller ships do long cruises and I don't think I'd want to be in an inside room going for 12 days through the Greek Isles. However, there are some larger interior rooms, just at a higher price! (and by larger, I mean, the same as the smallest on the bigger ships LOL). However, even the Ocean View rooms aren't much bigger--122 sq ft, on the Sovereign class, which has only one deck of balcony rooms (all Junior Suites (173 sq ft) and larger). You better pick a cruise that has a lot of port days because there's not a whole lot to do on that ship either!
I know people say "Oh, you never spend much time in your cabin anyway". Well, we did, for several reasons. Make sure you have at least a couch--I was looking at a Princess brochure for their newest ship, and the interior rooms don't have a couch; they don't even show a chair other than at the desk. Don't be surprised once you board. Spend some time on YouTube and on Google and get pictures (and videos) of possible rooms. On the Sovereign Class, the brochure picture for the interior room shows the bed pushed against one wall (so you get in either from one side or from the foot). This would drive me crazy and I'd have to have the "outside" half, so I can have the night table and access to the bathroom LOL.