How much better is it than Safari? I find the differences in browser performance so subtle nowadays that I lean towards whichever gives me the most seamless experience—-which, as a Mac/iPhone user, is safari.
For me it's mainly about synced history, open tabs on various devices (phone, tablet, computer), shared preferences, etc. The rendering engine is secondary to that in my list of priorities.
I have Firefox in the dock on iPhone and it's really great but random links, e.g. via messaging, get opened by Safari first.