Safari 11 outperformed Chrome, Firefox, and Opera for Mac.
A short time ago, it was being bandied about that Safari 11 would be the fastest browser for the Mac. It was, of course, conjecture at the time, but the benchmarks are in and Apple has put its money where its mouth is.
Not only did Apple say Safari 11 is the fastest web browser for Mac, but it went so far as to say it's "the world's fastest desktop browser". Macworld decided to run some browser benchmarks comparing Safari to Chrome, Firefox, and Opera, running the High Sierra public beta, and it turns out Apple wasn't just talk.
In eight benchmarks, Safari 11 handily outperformed the other browsers seven times. Firefox won out in the WebXPRT test, which is used to test HTML5 performance, though Safari still came in a close second.
Of course, take this with a grain of salt, since the other browsers are available for Windows, and Safari 11 is obviously optimized for the Mac by the people who made the Mac. That being said, if you're looking for the most nimble browsing experience once High Sierra rolls out, there's no question that Safari is the way to go.