For me, it's the ability to have Firefox Sync, Firefox's tracking blocker (although ad blocking isn't available unfortunately), and the familiar visual UI of Fi

For me, it's the ability to have Firefox Sync, Firefox's tracking blocker (although ad blocking isn't available unfortunately), and the familiar visual UI of Firefox. It's not literally a "skin", Firefox on iOS is actually a separate Apple-approved app. It's just that they're forced to embed the Safari engine rather than using Gecko for it.