TheQuantifiedScientist on his YouTube channel has great tests for many wearable devices and their sensors. His assessment has been very favorable for AW Ultra on HR, location and sleep when compared to Garmin devices: for sleep tracking Garmin is very inaccurate, for HR and location Fenix 7 and Ultra are identical. Fenix 6 and older are poor.

Blood oxygen and temperature seems to be quite inaccurate on both.