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

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I got frustrated with Fitbit after getting several faulty ones. I've had a Garmin Vivosmart 5 for 2 weeks and I'm delighted with it.
I've been with Fitbit since 2014 but the last year I've had awful problems with them. I've sent 4 devices back because they wouldn't charge or the band constantly becomes unclipped and they just sent another faulty device. I bought a Garmin Vivosmart 5 a week ago and so far very happy with it.
i also had a fitbit and left when google took over. i have a garmin vivosmart 5-it doesnt have all the bells and whistles of the other ones but it does the same thing and not as expensive.
Vivosmart 5 - simplicity and size
I have a vivosmart 5 which even though it's entry level, was a hell of a lot of money for me on welfare, but I've never regretted it. HR alerts and no subscriptions. The reason I went with it and not a huawei or no-name was because I read a ton around it before buying, and testing shows Garmins are more accurate. If I didn't have enough for a vivosmart 5, I would get a second hand/ refurbed vivosmart 4.
I have a Garmin vivosmart 5 and I love it. It is very small and light, just does the bare minimum. As someone else has said though, make sure to check with parents that there are no issues. The tracking of runs is fine, but it can easily spiral into more sinister territory from there.
I ended up going with the Garmin Vivosmart 5 when my the app quit allowing me to update my sleep for my Versa 2 and long before quit showing my step history. The connect app has the mountain hikes like the old Fitbit had. But fitbits was because you could view scenes from each venue. I left Fitbit because of the continuous degrading of the app.
I just bought the Garmin a few weeks ago after owning Fitbit for at least a decade. So probably not.
I like it. I think the Garmin sleep algorithm weights awake time too high. But in general I like it’d small on the arm.
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

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Garmin - Forerunner 255 Series

Ranked #1
Oura - Oura Ring Series