I agree with the cons previously posted. However, you can get a room with a king bed (I think there is an additional charge of approx $10/night, but so worth it, IMO). As for the large size of the moderates, we stayed at CSR on our last trip, and requested a building that was close to the pool and food court. This request was granted, and it worked out great.
As for which resort, I'd suggest CSR - DH and I are also without children and we are in our late 20's. We liked that CSR seemed to have a lot more adults w/o kids than other resorts we have stayed at - b/c of the Convention Center there. Anyway, the food court at CSR was a big pro for us as well. And we liked the theming and pool. Plus, they just opened that new nightclub. Haven't been yet, but I checked out the website, and it looks pretty cool.