Apple Watch Ultra 4 vs Garmin Fenix 9 Pro: I wore them both for a run with an electrical heart-rate monitor — and I'm excited to report that both watches nailed it

(Image credit: Future)

The Garmin Fenix 9 Pro and Apple Watch Ultra 4 are two of the best (and most expensive) smartwatches to come out this year. But just how accurate are they?

Much has been made of Apple's redesigned Health Sensing System, supposedly the most accurate ever on a wearable. It certainly measured my sleep well enough, and Apple says it tested its accuracy by pitting it against an electrical heart rate monitor — which, funnily enough, is my…