Here is an area where the Fitbit shines. It gives a summary of the specific exercise routine. It's heart rate measurement focusses on exercise whilst the ring focusses on sleep. Of course the Fitbit also has a screen readout showing heart rate, steps, floors, etc during actual exercise. If the Fitbit is paired with a mobile phone it will also show the GPS track and elevation if it is an outside exercise. For the Oura Ring you add an exercise as an activity tag.