If you are worried about battery performance, I can personally attest that Firefox is better than chrome in terms of battery performance.
Still Safari is the best in terms of battery endurance (its a VERY SIGNIFICANT difference). But then again its Safari, so you have to decide whether you want a capable browser (FF/Chrome) or a battery efficient one.
IMO Safari is a very capable browser. I switched to it long ago and found I didn't miss anything from Chrome. Experimenting with Firefox now because I love the containers feature, I hope we'll see it in Safari some day.
In my personal experience, other than Apple crippling the extension feature by moving them over to the App Store, Safari is a pretty damn capable browser. It's actually been rather interesting to see drastical improvements in it yearly, even the Mojave build's come with a serious performance boost. Firefox overall feels a lot slower than Safari with some exceptions. The only major killer feature I've noticed is the Devtools on FF.
Still Safari is the best in terms of battery endurance (its a VERY SIGNIFICANT difference). But then again its Safari, so you have to decide whether you want a capable browser (FF/Chrome) or a battery efficient one.