In Rome we stayed at and loved Portrait Roma. Location for us was perfect and a great breakfast was served every morning on the roof top. Service was exceptional and we loved our suite. Will definitely return there next trip!
Haven't stayed at the FS in Firenze, but on our last trip we were at the St Regis. Our suite (the Botticelli suite) was gorgeous and I'm certain considerably less than the FS. The service was wonderful and the location is an easy walk to the center of town. Something to consider.