Chiming in here as something that has both an Epix Pro and an AWU2 and hopes to rationalize to just 1 device. Also training for my 7th Ironman triathlon.
I also like some of the Garmin stats and reporting (training load & effect are 2 I like), but I actually have found compelling alternatives such as Superset Health. I've been training for my IM while wearing both for all activities & the trends on both the iOS apps such as SuperSet and Connect are extremely close. I've also found Superset gives me a good HRV trend value as well.
Honestly, I'm still not sure which I will end up keeping and which I will sell, but I'm ever so slightly leaning to the AWU2.
The primary downside, battery life, really doesn't hit me that hard as I work and train from home 95% of the time so keeping my battery charged while at my desk for 45-60 minutes a day is not a bother at all.
I absolutely love that the AWU2 heart rate data is as-good as my chest-strap (HRM Pro Plus) that I am forced to use with the Epic Pro as the OHR for the wrist does not do nearly a good enough job.
Swim HR on the AWU2 is good enough, the HRM-swim paired to the Epix Pro is definitely better, but also significantly more of a PITA to wear for swimming.
Strength training is the other place I am shocked at the AWU2 HR accuracy as so much more reliable than the OHR on the Epix Pro.
One thing I strongly prefer on the Epix Pro is the screen customization options for structured run workouts based on HR or Power Zones. On the Garmin you get a gauge visual showing you the intended range and your current as a tick mark. It's fantastic. The AWU gives you notifications & haptics, but I miss the gas gauge style indicator for target zone.