I use an iPhone 6 and I launch Skype and my app. My app launches in low resolution (seems like non-retina) and Skype launches in high resolution - status bar resolution stays the same as in home menu of iOS, while the status bar in my app seems "bigger".
The one on the left (mine) is clearly lower resolution. What could be causing that ?
Make sure you have Launch Screen or launch Images at correct resolution for iPhone 6 or 6 Plus, otherwise your application will run in 'display zoom' mode. (scaled up version from iPhone 5 or 4...)
See this SO question, you can either :