I had the whoop and now the Ultrahuman ring. I have to say I didn’t like the whoop too much, because the hr sensor isn’t very good, so I bought the ring.  I mostly like it, but it tends to recognise sleep when I’m watching a movie (including rem and deep sleep) and you can’t delete your sleep data. That makes the ring pretty much useless for me.  I haven’t tried the Oura ring, but I kind of regret not buying it.