I have only used Di2.
With my 1x system since I'm only shifting the rear derailleur, my Di2 battery lasts for several months between charges. I plug it in every month or two when I think of it, but it has never been less than 50%.
Etap uses smalller batteries mounted on the derailleurs, so they require more frequent (daily?) charging. I believe the brifters use small watch batteries as well, but those are supposed to last quite awhile.
Aside from that, I feel like you have more options with Di2, as most Di2 components are plug and play. I run an XTR derailleur with road climbing switches mounted on my drop bars.
Daily charging on Etap? LOLOL Are you kidding me? I have had my Giant Defy since Feb that has Etap and I've had to charge my batteries twice. The nice thing is with 2x is if the rear dies you can take the front and put in the rear. But I've NEVER had that happen. The AXS app lets you know when to charge them. Same with the shifter batteries, but most just replace them at the start of the cycling season. I had Di2 on my Specialized and I'll take Etap over Di2 any day of the week. I'm going Etap AXS 1x on my gravel build.