Safari use less CPU power than Firefox, chrome being the worst of them all.
It's even more obvious when watching video where safari will be 5 to 10 points lower than Firefox.
Harder to say when it's rendering page but the fact of the matter is that I tried both for years, Firefox always drain the battery faster.
>It's even more obvious when watching video where safari will be 5 to 10 points lower than Firefox.
Safari uses macOS for video so the points will be on macOS. Firefox uses it own internal video decoder. That is why image and video codec support on Safari is dependent on macOS upgrade not Safari.