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

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PW 3 is MUCH better than the OG. Sleep tracking works every single night. It charges much, much faster. The battery lasts longer. The UI is quicker. Apps update faster. Fitness tracking is more accurate.
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.
I'm using the Pixel Watch 3 with Golf Pad and it works great.
I use a Pixel watch. Golf Pad (the app I use to track my rounds) is compatible with the watch.
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.
I thought I would dislike daily changing, but I literally just charge it during my shower in the morning. Pixel watch 3.
Pixel watch 3 or 4. Both will last you comfortably more than 24h, especially the 4. Some of the best sensors and sleep tracking there is. A step down on health tracking but by no means bad is the oneplus watch 3. Much better battery life and tougher build.
Smartwatches aren't really medical devices, you should really consult with your doctor for advice in a proper monitoring device. That being said, if you have an android phone, pixel watches are hard to beat. Best heart rate sensors and continuous heart rate monitoring. ECG cannot be monitored passively as you need to close a circuit around your body, which means there's an electrode underneath the watch and the other is the crown, you must take spot readings with the opposite hand you're wearing it on.
The best sleep tracking outside of the oura and whoop are fitbit and pixel watches. If you want multi day battery life, it would need to be fitbit. Amazfit, garmin have great battery life and sports tracking, but mediocre sleep stage tracking.
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.

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Oura - Oura Ring Series

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Apple - Ultra Series

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Garmin - Enduro 3

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Garmin - Fenix 7 Series

Ranked #1
Garmin - Forerunner 255 Series

Ranked #1
Oura - Oura Ring Series