Fast, small footprint, highly battery life friendly. Bunch of extensions. Extensions support on desktop and mobile. Trustworthy repository of extensions. Special ad-blocking extensions API that delivers high performance and does not require extensions access to content of the page. Tab-groups out-of-the-box. Read later feature that is synchronised across devices out of the box, no third party service required. Bunch of privacy protecting features. Apple's hide-my-email thingy built-in.
That sounds excellent, actually. What's the apple hide my email thing though?
When you need to register on a website, you can opt-in into a random email that is generated by Apple. Something like cooker-huskies0u@icloud.com. They then setup a relay that sends everything it receives to your email that is registered with your Apple Id. You can cancel any of those emails whenever and never hear from that website again. There's a similar offering from joint venture of Fastmail and 1Pawword if you're not into Apple.
Nothing is faster or leaner. I have always been a fan of Firefox the underdog but it gets worse with every release in so many different facets. Performance has been terrible for a while now.