There are five single-story and only two 2-story, so I am not sure where you saw the opposite. I have stayed in both and prefer the single-story to the 2-story. The 2-story's living, dining, kitchen area is not as long as the single story. The area over the entry way and staircase is open, first floor to second floor ceiling. The master bedroom and bath that is downstairs is very similar to the single-story. The first bedroom upstairs, with two queens, has a little balcony area that you can step out onto and it overlooks the living room. All the rooms have balconies for viewing the lake area, including two in the living room/dining room area.
I personally prefer the single-story partly because I would rather not go up and down stairs in a villa, but the more significant issue is that the washer/dryer is at the very end of the hall on the second floor. Thus, the ones likely to be doing laundry, those staying in the master bedroom downstairs, have to go upstairs to do laundry. And the most likely time for them to do laundry while at Disney is late in the evening after the young ones are already in their rooms, but that is a serious problem because that washer/dryer makes quite of bit of noise and sits right next to the door of the second upstairs bedroom where those kids are most likely to be sleeping.
