They are comparable in size. The studios are laid out like those at OKW but have a queen bed and a sofa bed. The inn rooms are laid out like the other DVC studios (or a typical hotel room) but have two queen beds.
Inn rooms are all located in the main building while studios are all located in the three out-buildings. We prefer the inn rooms as we like a guaranteed view of the ocean.
The studios are a bit larger. Plus the fact that the couch gives you even more room. If on the 3rd floor there is a decent ocean view but not like the inn rooms.