Garmin
Forerunner 255 Series
Long battery, but wrist HR often inaccurate.

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I've tried Google Pixel and Samsung Galaxy and at the moment I'm liking the OnePlus Watch 3. They all have their strong points but the OnePlus has fewer weak points.
Yes. I never had any issues with mine. When my pixel watch acts up I charge up my charge 4
This is already possible on the PW1 and has been in use since the market launch. When I tested PW3, I only got to max 36 hours. So in stayed with PW1.
That's interesting. I was really disappointed and had the PW3 with 45mm but then returned it and continued to use the PW1. I'm rather impressed that she still holds out so well. Another reason is the constant changes to the charging port. I charge the PW1 90% via Qi because my third-party pad is ironically compatible. Now I wanted to upgrade to the latest model this year, but the new charging port makes sure that every case looks terrible or needs to be removed when charging... Hopefully the PW1 will last another year and we'll just get Qi2.
Pixel watch 4 is the first Pixel watch where I havn't had to ever worry about battery life, few minutes charge during a shower and it's good to go. This has also resulted in me wearing it pretty much everyday, all day. Previous Pixel watches I would often set down the charge and then forget to put back on. I would 100% upgrade from 2 to 4, even 3 to 4 is a significant enough improvement for me. I traded in my 1 when I got the 4 (still have the 2 and 3 that I hand down to family) and it was actually laughable to handle it again, it's tiny for a start with an even tinier screen due to huge bezel, I also remember the battery life was terrible. We have come a long way and I'm excited for the 5!
When I switched from PW1 to PW3 41mm, it was like a day and night difference. Both in terms of UI responsiveness and battery life. I think you'll be happy if you get a good trade-in deal and discount.
Pixel watch is the way to go. Excellent fitbit integration.
Garmin
Forerunner 255 Series
Long battery, but wrist HR often inaccurate.

Garmin
Forerunner 955 Series
Endurance battery, value king, but clunky UI.

Garmin
Fenix 7 Series
Rugged, long battery, maps, but HR and software can struggle.

Garmin
Enduro 3
Unrivaled multi-week battery, solar-charged, but bulky.

Garmin
Forerunner 965
Lightweight, vibrant AMOLED, maps, but wrist HR and swim issues.

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Oura - Oura Ring Series

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Apple - Ultra Series

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Garmin - Fenix 7 Series

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Garmin - Fenix 7 Series

Ranked #1
Garmin - Forerunner 255 Series

Ranked #1
Oura - Oura Ring Series