The short version
The Ultrahuman Ring Pro is the subscription-free flagship — one-time $479, ~15-day battery, on-ring processing. The Oura Ring 5 is the accuracy leader with the best app, at $399 plus a mandatory membership.
When the Ultrahuman Ring Pro is the right pick
You refuse a recurring fee, you want the longest battery in the category, and you’re fine being an early adopter of a redesigned ring.
When the Oura Ring 5 is the right pick
Accuracy and app depth are the priority, you want upgraded sensors and the most polished experience, and the membership is acceptable.
Also worth comparing
For the previous, cheaper Oura, see Oura Ring 5 vs Oura Ring 4; for other subscription-free rings, the Samsung Galaxy Ring and RingConn Gen 2. Full field: best HRV trackers.