Garmin
Forerunner 255 Series
Long battery; but wrist HR tracking is inconsistent.

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Fenix 6X PRO. Was a new open box item in John Lewis and marked down to £276 about 3 years ago. I’d been looking at an instinct and then saw this and jumped on it. Can’t fault it.
I’m actually going the other way: Fenix 6X Pro Solar to Apple Watch Ultra 3. I’ve always disliked the Garmin connect app interface, it’s just gross to navigate and use. There’s been a ton of bugs I’ve experienced with my 6X both on the watch itself and with the connection to the Garmin Connect app. In general the software experience with Garmin feels clunky and buggy. Most people don’t care I suppose since it (usually) works for just tracking workouts. The new Fenix line is way overpriced in my opinion, where the AWU is looking much more appealing. For the same price as a Fenix 8, I’m rocking an Oura Ring 4 for sleep tracking and AW Ultra 3 for everything else. It is far nicer to track your sleep with an unobtrusive ring rather than a bulky and uncomfortable sports watch (whether Garmin or Apple Watch). The AW also has satellite and cellular, which is even more expensive with the Fenix 8 Pro. It’s a goodbye to Garmin for me. I’ll keep my Fenix 6X if I ever need to do a super long gps recording, still works.
I have a Garmin Fenix 8 AMOLED 51mm, I had about 40% left after my 100 miler a couple months ago. I was previously on the Garmin Fenix 6x pro but noticed battery life wasn’t last quite as long as it used to so I upgraded
Fenix 6X Pro because my previous Garmin watches were Forerunners that didn't last very long before they began having bluetooth issues. I was really angry to deal with that through two watches after only a year and a half on each watch, so I thought I'd buy the flagship to give Garmin one last chance, and it's been an absolute TANK for 3.5 years now.
Garmin has better durability, fitness metrics, and battery life. Pick the Garmin every time if you are looking for a fitness watch. If you like the smart watch integration into your Apple ecosystem, go Apple. Currently sporting the Fenix 6x Pro Solar and absolutely love it!
Just moved from 6x Pro after +5 years to an Epix Pro Gen 2. I know it's not the latest o/s but new right now they are half the price of a Fenix 8, half the risk and no regrets. Not a huge difference but feels fresh with a few newer features and love the Amoled screen. The battery is great.
Garmin
Forerunner 255 Series
Long battery; but wrist HR tracking is inconsistent.

Garmin
Forerunner 955 Series
Best value, clear MIP screen; limited smartwatch features.

Garmin
Fenix 7 Series
Durable, multi-week battery, flashlight; high price, buggy software.
Garmin
Instinct 2 Series
Rugged, solar multi-week battery; bulky, small screen readability issues.

Garmin
Enduro 3
Multi-week solar battery, lightweight; but bulky form factor.

Ranked #1
Oura - Oura Ring Series

Ranked #1
Apple - Ultra Series

Ranked #1
Garmin - Enduro 3

Ranked #1
Garmin - Fenix 7 Series

Ranked #1
Garmin - Forerunner 255 Series

Ranked #1
Oura - Oura Ring Series