The only possible way that I can think of the Rainbow rooms being larger than Ali'i is if they were a corner rooms comparing to an Ali'i standard. I've had a corner room in the Rainbow and Tapa tower. One year because I booked during one of busiest times of the year, I was placed in the Tapa tower at check-in. I wasn't a happy camper, but when I saw the corner room I was pleasantly surprised. Really good size room just like the Rainbow corner rooms.