Actually IOS has come a long way from being wall gardened to some what open to other sevices. Since IPhone 6 I haven't looked back or used my android device as my primary device. Since the first iphone I have hated nothing but the email, calendar contacts apps etc. atleast now my biggest issue is solved with outlook email app, google hangouts for my google voice account.
Stability, 2gb of ram on my iPhone 6s means no more slow downs. I have had used atleast 20-25 android handsets until my last ones samsung s5 and nexus 6, IMO biggest issue about android vendors is they use cheap components to drive costs down like sd ram or flash memory(they deplete after few million reads unlike apples proprietary and high quality ram/flash memory and battery). Thats one reason why android phones crawl or have battery woes after a years usage. Try IOS 9.x and you will never go back to any other device. Smoothness, stability, camera, apps, tight integration with various services, some neat features like safari ad blocker and night shift are welcome additions