If you aren’t jailbroken, alternative browsers are slow, Apple’s doing
If you are jailbroken, as someone stated above, Nitrous makes 3rd party browsers fly
Personally, I use Mercury Pro- far superior to Safari, like it better than Chrome
advantages:
1) settings in app
2) has tabs and gestures
3) can sync bookmarks with firefox or chrome
4) can change user agent (can act as desktop browser)
don’t see any reason to use safari
5) can edit text size in easy to access settings