I'm going to differ with most of the comments here. I'm a solo traveler who did an aft balcony last June in Alaska for the first time. The balcony was very deep making it larger than a side balcony; however, it's also a long way (relatively speaking) from the cabin to balcony rail. Being that I'm always looking for whales and other wildlife to photograph (even from the ship), I was spending a lot of time walking from cabin out to the end of the balcony.
Also for photography reasons, I'm also very interested in knowing what is ahead of me. The aft balcony was bad for that.
This year its back to a side balcony for me.