To get reliable numbers, I measured both apps twenty times and calculated the averages. Furthermore, I closed all running apps on the devices, disabled background refresh, and put the device in flight mode. I did the measurements on iPhone 5S, 3rd generation iPad, and the retina iPad Mini with the latest version of iOS7.
The results for the total load time (CSS and JS) on the three devices are shown in the figure below. There isn’t much to add to the image, except stating that the minified version loaded around 10% faster (or, that the non-minified version is 11% slower). The differences are statistically significant (Student’s t-test) and most probably not due to randomness.
The Takeaways and Conclusions
So what can we learn from the results? I can definitely say that the minified versions load faster. And minifying the resources offers an easy way to shave off 10% of the load time. Though, in absolute numbers, the time saved is not very much. But every millisecond counts and can effect your apps financial bottom line. If you are already using some build tool like Grunt or Gulp in your development process, adding a step to minify your code should be simple, so there is no reason not to minify and make your application faster.