This is a great category! It is deck 2 midship with the large portholes. If they don't have any 9B rooms available for your party size, you will likely get a 9A forward room on deck 5/6/7.
For the Wonder/Magic: We normally stay in a 9C aft (at or slightly forward of the aft elevators)--which is also on deck 2. The 9B rooms have a slightly larger porthole than the 9C rooms we've been in. Most of the 9B rooms only sleep 3, which is one reason we've been in a 9C. While I have loved our 9C rooms, I'd be wary of doing a GTY rate with them as I don't want to be all the way aft or all the way forward, I like picking our 9C room. I'd do a 9B GTY though--midship, so no worries about extra ship movement!
We find deck 2 very easy to get places--up 1-2 flights of stairs to restaurants/clubs, promenade, etc and easy to get an empty elevator to go up to the pool deck! Also very convenient at ports as you're usually getting on deck 1, no need to wait for an elevator, just go up 1 flight of stairs!