This was our first cruise with a balcony. We selected a cabin (thanks to advice found on this site) that was for handicapped, wheelchair accessible. The cabin and balcony were quite a bit larger than our travel companions who booked a balcony cabin also. While you run the risk of having a last minute change of cabins, if it is needed by a truly handicapped person,most of the time it will not be.
Vibration:
My first complaint would be the constant vibration through out the ship. While some areas were better than others, the dining room (aft) was like sitting on a washing machine. I don't know why this was, but I assume there was something major unbalanced somewhere (engine?). Half of the ice machines on Lido deck, did not work. Very annoying to have to find ice for you drink on a hot day. Perhaps they are cutting back on maitainance or repairs.
The handicapped cabins are quite roomy. Be careful of the "emergencyy pull cord and push buttons. I accidentally set them off twice.