My Cabin 337 was one of 5 single cabins on Legend; there are 2 on the top deck, 2 on Deck 2, and 1 on Deck 1.
My #337 was adjacent to the library at the stern of Deck 3, and I loved the location. At a moment's notice, I could pop into the library and out a door to see or photograph anything on either starboard or port side of the ship. I'd guess that the other single on Deck 3, #309, is an equally good location and would mean less walking to the lounge or dining etc.
The cabin design and layout are good. Bed is a couch that converts to a bed, but this was very comfortable and resulted in more floor space, which I appreciate since I do yoga stretches each morning. I loved having the French balcony for fresh air when I opened the slider; I had it open a bit every night. The climate control in the room worked beautifully, including an "off" position for times I wanted the slider open.
There are outlets for both U.S. and European plugs, so charging camera batteries was no problem, nor was there a need for a converter.