I would definitely chose the St. Regis. The Ritz is terrible and although I hear the Mandarin was just renovated the location in not great. The St. Regis has by far the best rooms. I find the rooms at the FS to be very dull. Also, the pool is much better at the St. Regis. The FS is connected to the Sports Club LA so the pool/gym tends to be very crowded.