Of the two, I've only stayed at the MO ... we liked it a lot, although it's not perfect by any stretch.

Things we liked about the MO - a fairly quick taxi or tuk-tuk ride to and from town, very generous FHR upgrade and amenity (a 5 or 6 course lunch), very new property and our villa had loads of space and a plunge pool, food quality was excellent, my wife thought the spa was top-notch and rated her treatment at the property more highly than treatments at the Oriental BKK.

Cons - the plunge pool was really small - more like an unheated jacuzzi, so we rarely used it. Some of the furniture wasn't very well chosen - none of the outdoor seating that came with our villa was especially comfortable.

Finally, and this may be a pro or a con, depending on your POV, but we were surprised by how many families there were - many many kids, mostly well behaved but there were times when our tranquil enjoyment of the sunset was interrupted by kids from a neighboring villa noisily enjoying their own villas pool.

All in all, I'd recomment MO wholeheartedly for families looking for a luxury experience. For couples, it really comes down to value for money - we'd stay there again but that's in large part because the cost of a similar villa at the FS would be much, much more.