We stayed in both and prefer the one floor. We enjoyed the two story, but the one floor was better for us. One of our sons slept on the pullout in the living room, and in the one floor it's a good distance from the dining room table. In the morning, you don't feel like your going to wake him up, while in the two floor it's much closer.
We also liked having all of the six balconies on one floor, and they seemed larger than the two floor balconies.
The two floor had the washer and dryer in the hallway upstairs outside the studios, while the one floor has a seperate large laundry room outside the main bedroom with a sink, and folding table.
The two floor had a balcony looking over the living room, which our kids enjoyed, but it just "seemed" smaller. We did like the two floor, but I guess we were just spoiled with the one floor. This past trip we actually requested the two floor just so we could experience both.
We usually have friends over at night, and you definitely have more room to entertain in the one story.
You will enjoy both, good luck with your' choice.