I agree with you. My s8 is on just regular HD and my eyes could never tell the difference! Plus just like you said, I'd rather have the battery than anything else. The phone runs cooler. The s8 owners to really tell the difference in screen resolution in my opinion are the gamers with the quad HD resolutions. I also have my brightness set to automatic so the screen is viewable in the direct sunlight.I don't see any discernible difference and would rather have the battery.
I have perfect 20/20 vision, and my eyes still can't tell a difference of the higher resolution settings. I mean I tried full HD or for a little bit but then just scaled it down. Still looks great to me!My old eyes can't really tell the difference, so mine is just on HD.. Maybe if I did VR or watched movies etc...
Exactly for VR content, gaming etc the higher screen resolution are perfect. But honestly for regular phone/application usage most people just don't need it. Only turn up the resolution to the phone, if you're doing VR, it slaughters battery. I tried my dad's Google cardboard out a few times with my Galaxy s8.FHD. I can't tell the difference. I think these ultra high resolutions are good for VR or 4K content but everyday use... Just a selling point. I mean, c'mon, you guys seem to be doing it just because it's there. More power to ya, though!