My wife and I upgraded from the AW3 - definitely much worse battery life. We both got easily 2 days of usage out of our watches.
Now, my wife's AW5 40mm GPS dies in the middle of the night if she doesn't charge it after the morning at least once.
My 44mm AW5 GPS will be at 20-40% in the morning after a full day and evening, but I have AOD off, noise off, Siri off, etc... I turned all this (except AOD/Noise) off on my AW3 so this is normal for me.
After reading this thread - I am now turning off fall notifications and turned off 80% of background app refreshing to see how that goes.
I really want AOD on but like some noticed in this thread, the raise to wake sensitivity is easily 2-3x as sensitive as my AW3. Drives me nuts though, to have to tap the watch when it buzzes with raise to wake off so... I think that'll have to stay on.
Also agree with the thread that brightness monitoring is always changing - almost always too bright even though I have brightness all the way down.
Since I charge every morning, I'm happy. My wife isn't too happy but if she turns off AOD and some of the other unnecessary things (noise/fall/etc...), then I bet she'll get similar to my usage.
We're not even considering returning our AW5s. We're pretty happy with them. We will be putting our extra AW chargers at work though. If we had AW4s we'd be unhappy I think.