Activity tracker….

Overgeneralizations:

If your real-life friends have a particular brand, and you like doing challenges with your friends, get the same brand.

People who are very Apple-centric in their other electronic devices tend to like Apple Watch for its smart watch functions and integration with the environment.

Multisport/multi-activity exercise-centric people often go for Garmin. They have some good built-in features for sports, and also quite a list of integrations with other sports-orientate apps.

Fitbits have a little worse reputation for dying young compared to some of the other major brands.

Major issue: What features do you need? Is your main goal MFP integration for calorie estimation, or something(s) else?

I use a Garmin, recently moved from Vivoactive 3 to Vivoactive 4. I'm an on-water rower, and it has some good performance tracking features for that. For rowing specifically, I need it to integrate with a chest belt for heart rate, because there's too much arm flexion for a wrist-based heart rate monitor to handle. I wanted a device that didn't require me to carry my phone when working out. (I don't like taking a phone out on the water, or having it in Bluetooth range every minute for some other activities.)

I'm old, used to wearing a watch, still prefer one for time (vs. checking my phone for time), and I need a big time display because my eyes aren't that great. I'm kind of oblivious, so I need something tough/durable, but as a li'l ol' lady I'm OK with a sports-watch look but don't necessarily want something that makes me look like a wanna-be Navy Seal/Commando. Long-ish battery life is a plus. I didn't think I needed smart watch features, but I like that'll notify (wrist vibrate) if I get a phone notification when in bluetooth range: It means if I'm expecting an important call/text, I can put my phone in my purse/pocket in social situations but not miss the important message.

What for specifically is important to you?

I have a rather expensive garmin watch. Don’t care about smart watch functions, want long battery life and their numbers work for me mostly. Note, this IS individual and might not for you. Also, like other devices their walking calories are shite

I have a Garmin Vivoactive 4S and I like it.
Step count seems pretty reliable, I like the optical HR sensor (for when I'm not exercising, estimating my resting HR for example) and the fact that I can pair it with a HR chest strap when exercising (more reliable).
There are a lot of in-built exercise types, I mostly using (treadmill) running, strength training and indoor rowing.
The TDEE and running estimates are a bit low for me, but still a very useable basis. Battery life is pretty good too, I usually charge my watch once or twice a week. I need to charge daily when doing day hikes though (the GPS sensor does use a lot of battery).

I’ve been using the Apple Watch since it first came out. Currently using the Apple Watch Ultra to track my workouts and daily activity.

I have a Samsung watch and would NOT recommend it. It pretty much constantly says my heart rate is 75 despite multiple other devices including hospital monitors saying my heart rate is 50-60's at rest. Surprisingly it also claims my heart rate is about 75 whilst working out too. Regardless of how intense and again when other monitors disagree. The only time it seems to change is when I am asleep. The watch sensors are clean, it is plenty tight, and fully charged. It just isn't accurate.

It is also fails to accurately track activity. For instance, Google fit will show my 90 minute walk. Samsung logged me as having walked 15 minutes, stopping, walking a few more, stopping, repeat. There was no stopping on my walk, so it is just wrong.

Because the above doesn't work, the calories burnt is just a made up number.

It does some other things, but also not very good.

Like I said, I would NOT recommend it to anyone. I wish I never bought it and am looking for something better.

I liked my FitBits many years ago, but they seemed to last under 2 years (costing less than $150). I also liked my Garmin Vivoactive from about 5 years ago, which still works, mostly. But I upgraded to a Garmin Fenix 6s about 2 years ago when it went on sale, and it's been perfect. Battery life is about a week, and it tracks just about any activity. (Including Surfing, which I just did!)

My suggestion for anyone who is starting with a fitness watch and doesn't know if they'll like it is to buy a used or refurbished on on Amazon, Ebay, or Swappa. Either it will be all you need, or you'll decide it's too much of a hassle, or you'll decide to upgrade in a year. In any case, you won't have spent that much on it.

Now, I have friends that love their Apple Watches, but you need to charge them about daily.

I just got a fitbit inspire hr 2. For 56 euros. It tracks heartrate accurate, I know this for sure as I have an medical implanted heartrate monitor, that was used during corona to see if I really needed surgery asap. I did, so the issue got fix after 6m but the battery life is 3 to 5 years. I picked this fitbit as it was waterproof and able to track swimming.