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
For what it's worth, I don't feel like my opinion has changed with iOS 9. iOS 9 runs better on my (bit dated) Apple devices than iOS 7 or iOS 8, but it's nothing closed to how it ran with iOS 5/6. The services and some customization options have improved, but it's still a pretty locked down ecosystem. If the manufacture doesn't allow you to do what you and fights allowing people to get simple things like root/admin that's where I draw the line. Although, I admit that WP7/8 wasn't much better, but at least there you had some more flexibility with developer tools. Of course, when I think of openness my first thought is of Meego and the Nokia N9, but that was short lived, unfortunately.
Hardware on Android devices will of course range in cost and quality. A $50 Android Tracfone isn't going to be nearly as good as a Galaxy S7. There are also phones like ones from OnePlus, Meizu, Oppo, and Motorola, which aim to provide the best phone for your money.
I'm not sure I'll return to an iPhone any time soon, although I find the iPhone SE has most of what I wanted in an iPhone (smaller screen, a bit cheaper, hardware performance to match the other models). It really comes down to what you are looking for. The good thing is there are lots of good choices out there. Neither option is without its drawbacks. Unfortunately that doesn't include Windows Mobile phones for now.