I am currently using an iPhone 6s and I just upgraded probably about a month ago from my 5s. The only reason that I upgraded was that the battery on my 5s wasn't lasting to long and it seemed to drain and go down all the time when it was in standby. I tried restoring it and everything else and the battery was still going down. I installed a battery app and it said that it had 780 charge cycles on it. I even went to my carrier and they restored it and it still was going down. They also tried some other things to it and it still didn't make a difference. I decided then to upgrade and I was torn between the se and 6s. I was considering the se because it was cheaper and I absolutely love the form factor of the 5 series. I decided to go with the 6s because of 3D Touch and how much iOS 10 relies on it and I figured that future versions of iOS would rely on it too. I also decided to go with the 6s because of the increased color saturation and the bigger display. I am happy with the 6s and feel the screen size is just right for me and hope to get quite a few years out of this phone. I really loved the 5s though and it didn't feel like it was slow on iOS 9 and it was a great phone. I still have it and if my 6s battery completely dies or something happens to it, I might try going back to it before upgrading again.