I would say not much of a advantage using Safari on either iOS or macOS.
The thing is iOS will only allow you to use webkit to render pages. So Chrome, Safari, Firefox all basically use the same thing. They might handle bookmarks a bit differently but the engine that makes it all work is webkit. And you must use webkit on iOS if you make a browser.
On macOS is it a bit different. Most browsers use a different rendering engine. So there can be a pretty big difference between them.
I can’t think of a single feature that makes Safari better except it is slightly faster on iOS. I use Safari on iOS and Firefox on macOS.
There is no killer feature that would make me switch to Safari.
However, back when Safari was released for OS X it beat the shit out of every other browser. Lightning fast and had the best standards compliance.
Now I would just say all browsers are pretty good. Except Chrome. Fuck using a browser made by a advertising company.