The app I using for this is Streaks

So it looks the the Oura ring tries to “analyze” the data in addition to just tracking it- it looks like it tries to give you a sleep score, readiness score, and interpret data to give you insight on your stress levels. If the data is all you care about I would do some research on how accurate the data capturing is for each device, but just as a quick glance it looks like the Oura ring has more “features” when it comes ti data tracking. But if you care about other things than just the data, of course it’s important to note that the Apple Watch has many more features than the Oura Ring just around the board. To me it seems like it would be more of an issue of if you would rather wear a ring or a watch, and if the little bit more robust (it doesn’t seem like it’s that much more tbh) data gathering is worth it to you to throw out other features that the watch would provide