Everything Apple Pro did an amazing side-by-side speed test comparison of every model of the iPhone from the original to the latest iPhone 7.
The comparison tests things like boot time, HTML 5 compatibility, and app load times. It also compared the audio output, heat output, and various camera tests.
ALL iPhones EVER Made Comparison! 2016 Edition Part 2. iPhone 7 Plus vs 7 vs SE vs 6S Plus vs 6S vs 6 Plus vs 6 vs 5S vs 5C vs 5 vs 4S vs 4 vs 3Gs vs 3G vs 2G!