The two Garmins I had (935 and Fenix 6) had way better battery life than my AW8 or Ultra 2, not even a comparison. I could get well over a week, sometimes close to two weeks, in between battery charges. I use my watches as golf watches, so I'm using 3-4 hours of GPS and screen time 3 to 4 days a week in addition to all the normal daily usage.
The problem I had is that with that kind of battery life, I didn't pay much attention to checking battery status or charging it, and got caught flat-footed a few times where I was heading to play golf or go for a run and noticed that I had <10% battery left - which wasn't enough to get me through, and Garmin watches don't fast charge. With the Apple Watch, I know I need to charge it every night so it's a habit and I'm always aware of where my battery % is - which may seem like an inconvenience, but it's actually more convenient to me because it makes it a routine. The AW8 can make it through a full day with a round of golf included, although it's usually pretty drained by the evening when it's time to charge; the Ultra 2 can make it a day and a half or so if I have a round of golf in there (easily 2 days without it), so I still top it off in the evening so it's fully charged for the next day.
Garmins have way better battery life because their display is primitive compared to an AW, and they have far fewer battery-consuming features than an AW does. They're good fitness watches (although their HRM sucks compared to an AW, IMO), but crude and severely crippled as a smartwatch compared to an AW. It's a tradeoff that is acceptable, even necessary, to a small niche group of extreme "ultra" athletes who need the long battery life to get through their training/competitions, but it's not a deal maker/breaker for the vast majority of people unless you just hate charging a watch that much.
