For the reduced price, I would take 11 if it is available, especially if you are a couple sharing the room. I used my room on the Cat strictly for sleeping, showering, and storing clothes. The boat is so nice and spacious, you do not need anything besides a bed.
You will have a great time, the crew, scenery, food, activities and atmosphere are incredible. The diving is nice, we lucked out and got lots of sharks, turtles and stingrays, but the reefs are a little underwhelming. Hopefully, you get to dive more in the marine park than we did (we had a very windy week and hide to hide behind Eleuthera). I would definitely go again- the ease of access, quality of crew & boat, and overall good diving made it an awesome trip.