I mean, is there no one on YouTube who has two S21 Ultra/S23 Ultra devices and can compare their battery life, just like with iPhones?

Edit: Im talking about One UI 5.1 vs 6.

Does anyone know why there are no existing videos, but there are 100 where people talk about how they FEEL like their battery got 400% better or worse, using different apps (for different time) for their comparison?

People talk about how they got doubled theire screen time, which is not possible, unless Samsung removed a secret-bitcoinminer which they have installed before. A software update will not make your battery go from 5.000 mAh to 7000 or 12.000 mAh, therefore a sot from 4 hours to 7 hours is just not possible.

Also it is a difference if you use Snapchat for 1 hour or 20 minutes. Therefore you can´t say if the battery got better or not.

You´ll have to

Same Hz, Same settings (wifi, bluetooth) as before and use the same app for the same time, while having the same background (because of black pixel save more battery) otherwise its just wrong. :)

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Im reading a lot recently about this and its cool to share your experience, but sometimes its just wrong