My first purchase GW4 40mm was very hastily done. I mainly wanted a watch that could stream music independently and was under the assumption that only Wear OS watches were capable of that(on the Android side). Couple that with the high initial cost of Garmin, and I overlooked it. But it is a mess if you have to put a watch on a charging Puck for 2 hrs daily(that only had 5W wireless charging).
Unless Wear OS really changes it's direction in the next few years(and I hope my relatively newer GW 6 Atleast lasts for 3 years), I would be looking for a Garmin as well.
The 45mm GW3 had 340mAh battery, which was a downgrade from 472mAh battery on the original Galaxy Watch. The review at GSM Arena mentioned that the 45mm variant of the original Galaxy Watch yielded 2.5 days under moderate use. Samsung's quoted time is/was longer though that might be under ideal conditions.
I personally used only 4 and 6. Whilst the latter has a bigger battery owing to the larger size and plows through almost 2 days with AOD on(hardly any notifications or continuous Hr though), the 40mm GW 4 barely crawled a day for me.