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

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I just went from a Fenix 6s to a Fenix 8, and I'm really glad I upgraded screens from MIP to AMOLED (along with size to 47mm). Not as important to everyone, but I think it's something worth comparing and considering.
I'd suggest creating a list of features in your AWU that you can't live without, then seeing if Garmin can support it. This will help you decide if you'll be ok with the tradeoffs and also potentially help you assess what you truly "need" out of a watch. I would also assess the features on the Garmin watch you're interested in, and see how that compares with the AWU. You may end up with things you "need" or really want that the AWU doesn't have (e.g., battery life or flashlight). Afterwards, assess your tradeoffs both ways. You might find one is missing more than the other, or one is missing more important things to you. I got the F8 (AMOLED 47mm) recently and now I don't know how I was even surviving with only the 9 days on my F6S before this! I forget the last time I even charged it. The flashlight has also been very helpful for random things. Also, I would recommend sticking with an AMOLED display, I think you'll be very underwhelmed with a MIP one coming from your AWU.
I dumped my 6s for an AWU3 - zero regrets. The only thing I miss is native, on-board mapping.
Definitely keep the Fenix 6X. My wife is still using a 6S and happy with it, I'm using an Instinct with a 7X for hiking. Apple Watch is just way too distracting. The biggest problem isn't even the horrible battery life and having to charge every day, it's the feeling of being a complete slave to your phone. Having a phone on your wrist just isn't good for your mental health with all the constant buzzing and notifications. It creates so much stress. Sure you can turn off most of the notifications but at that point you're just using a worse Garmin.
Definitely keep the Fenix 6X. My wife is still using a 6S and happy with it, I'm using an Instinct with a 7X for hiking. Apple Watch is just way too distracting. The biggest problem isn't even the horrible battery life and having to charge every day, it's the feeling of being a complete slave to your phone. Having a phone on your wrist just isn't good for your mental health with all the constant buzzing and notifications. It creates so much stress. Sure you can turn off most of the notifications but at that point you're just using a worse Garmin.
Fenix 6S. Its been great for five years and has seen many miles around the world, but the altimeter hasn't worked for almost a year and that has impacted data quality. Have to recharge every 5 days instead of 8. I have small wrists and I hate that the logical next upgrade is the 8.
I’ve worn the Garmin Fenix 6S daily for almost six years now. Recorded hundreds of rounds of golf, running, hiking, skiing, boating, swimming. Tracks sleep scores every night. Tells me when I’ve had too much to drink. The sapphire screen is damn near indestructible. And it still gets 5 day battery life and charges to full in half an hour. I keep eyeing an upgrade but the watch still works and besides the replaceable band, looks new. The Fenix is an incredible piece of engineering.
For years I wore a Fenix 5s and then 6s in rose gold. I have an Epix Pro Gen2 now which has a nice amoled display like the current Fenix 8 series. The Epix 42mm (same size as the Fenix s series) came in soft gold which is also attractive for women. I almost got that but I wanted a little more battery life so I went with a 47mm this time around. But the 42mm would been just fine and if I had a job where I have to dress more professionally I would have gone with that one. The Epix pro gen2 is the last generation and while not cheap, is an excellent deal since it does almost everything the current Fenix series does (certainly everything your wife wants) including the current gen HR sensor and has an amoled display. The Venu watches are okay but are more lifestyle and not true sports watches. I briefly had one and it wasn’t near as durable as the Fenix/Epix. All of these had sapphire glass because I’m not the most girly girl and am tough on my watches.
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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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

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Oura - Oura Ring Series