Well, I have a kinda good grasp on what each OS can do.
As far as functionality in the OS, I do think android does more. You can choose defaults for web browsers, email, text messenger, etc. which I think is cool. I also think changing launchers is pretty cool. I think it's neat that you can change the feel of your phone on the fly. Also, I do like that it's more open. In the sense that I like that I can incorporate it into a mix and match tech work load and it should work with most things. Of course, I guess iPhones the same. But I still feel like you feel you need to use it with other Apple stuff instead of a mix and match setup. But this may be my weird skewed perception.
However, android still has this multi headed hydra thing that I don't like too much. I know that having all these OEMs make android their own way is considered a good thing by a lot of android fans, but I find it annoying and frustrating, especially when I really like the look of material design, but my htc phone won't get the look because HTC does their own thing. You get the backend stuff and behind the scenes stuff, but still I'd like to get that great looking design. And I can't unless I root and put in the GPE ROM or something, and I'm not gonna do that.
Also, the performance still isn't there. You still notice little hitches in android and frame rate dips in games compared to iOS. But it's better than its been in the past. Also, I do think the quality of apps is still better on iOS, but I also do t think android apps are so bad that this may be a deciding factor.
Also, the gorgon knot that is android software updates on carrier phones goes without saying in its frustration. But to be fair Google has done all they could and have made their stuff more modular and put most of the apps in the App Store to be updated instantly. Also, play services does great stuff to help this too. But still, big releases like lollipop remind me of the update frustration with android on non nexus devices.
And as far as tablets go, I still think iPads are best.
So those are my observations of both. I do have to say that I'm used to the m8s larger screen now compared to my 5S that's it's hard to go back I think. But that's what the new iPhones are for. But those aren't a option right now.
So again, both OS's have their appeal to me. I think though that since I don't root or rom maybe the polish of iOS appeals to me. I'd rather have that and fast updates than random updates times and weird little hitches. But then I think about the agnostic nature of android and that I can choose how it looks and works with root or hacking, and that appeals as well.