Browsing via Opera Mini is faster because it makes use of server side rendering, which significantly compresses data before it reaches the device, also resulting in less data usage. You can compare the speed of browsing via opera mini and safari on identical iPhones over edge in the youtube video below.
Opera Mini for iPhone also includes Tab Browsing along with many cool features. This app is really worth trying and will definitely be the better alternate for the default safari browser for iPhone.
Please note, the app is not approved by Apple yet, so lets hope when we are able to use it!