Garmin
Forerunner 255 Series
Long battery; but wrist HR tracking is inconsistent.
Running these analyses costs money. Buy through my links to help keep lights on! I may get a small commission.
I returned the mk3i 43mm. It’s heavy for daily use and the screen is small for diving. So trying to do everything but it’s not good at anything. I got the descent x50i instead and just use the super light Apple Watch 10 for everything else. The Apple Watch Ultra was also too heavy for me. To me heavy is ok for just a fashion watch. But for a fitness watch I don’t like it.
I have a Garmin MK3i (43mm) that also does everything you will ever need a fitness watch to do. I decided on getting a dive computer that did fitness watch stuff instead of a fitness watch that did dive watch stuff, cause, you know. I really like my MK3i, it is excellent underwater, and I cannot recommend it enough.
I have a Garmin Descent in the 42 mm and no AI (it wasn't available in the MK 2 in the 42mm version, I think in the MK 3 it is now) but it's only a bit thicker than the Forerunner 945 I had before. I wear it 95% of days and it does everything I want for diving and other activities.
I am happy with my Garmin Descent G1. I use it for freediving, SCUBA, hiking, running, cycling, walking and other shenanigans. I have only used it for Air in SCUBA. Others might disagree with me but I would still have a dedicated dive computer aside from a smartwatch. For SCUBA purposes, I mainly use my Descent G1 for logging purposes and surface navigation. There is the newer Descent G2 now but it comes with a OLED screen which I dont like because battery life is shorter and it blinds me at night.
Descent g2. I dive 30 or so times a year. The descent mark2/3 feature of tank pod didn’t appeal to me greatly to justify double the price. In hindsight I probably would have gone with the g1 for the battery life, at the moment I get 2/3 dive days. Or a week of general wear and activity tracking. I love the g2 though, great all round watch, all the features I need, the amoled screen has amazing visibility in and out of the water
I just got a Garmin Descent G2 and I really like it. I have tiny wrists and it’s yet not too much for every day and still seems very functional for diving (I’ll let you know Friday, which will be my first dive with it). I also use it for runs and gym workouts. My husband has an MK2s he’s been using for three years and he loves it.
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