First image shot with my new iPhone 6s. My old phone still worked, but it was a 4s with only 8GB of memory. I was constantly having to dump apps, delete photos and play with compromises because of the limited memory.
The reason for the 6S instead of the regular 6 is simple: resolution. I wanted the better camera. I know I will be needing to use this phone for another 2+ years and so I got the highest resolution (12 MP) and the largest memory option available (128GB).