I have both an Apple Watch 8 and the Garmin Fenix and I use the Fenix for sleep tracking. I find the Apple Watch to be too general with the stats. The Fenix gives a lot more detail. You can debate if the extra detail is useful or not. I also like the heart rate variability tracking with the Fenix (it seems to mirror how tire I feel pretty well). Lastly, the Fenix can hold a charge for several days. I can use it to sleep track and run and repeat and it charges quickly. If I sleep track with my Apple Watch, it may not have enough battery for the rest of the day. I run with both -- the Fenix for running specific tracking and the Apple for calling friends, listening to Audible, or podcasts.
That would be an understatement, are you running/cycling a lot outside, or is it a smaller model (thus small battery because physics)?
Mine (Fenix 7) holds charge for 15 days minimum and that's with tracking workouts 3-5x/week (no GPS though, winter so I treadmill for runs). On a couple of months where I didn't do sports it held up 25-30 days.
I have SpO2 tracking disabled because it's quite battery intensive and the only use for it would be high altitude acclimation, although I must admit I looked at it during my "stop smoking" process.
my experience with garmin (vivoactive, not fenix) was that they had all kinds of precision and detail, but it also didn't even notice when i got up to pee in the middle of the night - just a straight line through the graphs as though i hadn't woken up at all. that was the end of my trust in their sleep tracking.
Mine reliably notices that I woke up and immediately go under when my wife comes home late in the night, which happens basically every day (because bartender) so I get somewhat statistically significant results in that regard.
The Quantified Scientist does very detailed, measurement-based tests on all sort of smart watches, you might want to see where your device stands in his charts in terms of accuracy.
my garmin was really good at picking up my heart rate. there was one time i had it in a waist pack, and i was wearing a chest strap that was not paired to the garmin, and the garmin managed to pick up a pretty accurate heart rate for most of a bike ride.
