Stayed at MO in August and visited FS.
The MO is more modern and much more private. Also more expansive. The FS looked very mid-90's. Is that when it was built? It seemed a noticeable step or two down in physical plant quality.
And while I liked the MO very much, it certainly is not a replacement for the southern resorts like the Amans or the FSKS, etc. It is more like the ideal home-base for exploring Chaing Mai and the rest of the region.