I have a Nokia 620, an iPhone 5 and a (broken) HTC One X
I got the 620 as it has all the features of the higher models at a super low price. (All the HERE apps, City lens etc).
I find useability better than iOS. I am not completely convinced by the tile system, as I find it more difficult to find apps, and often go into the full list instead.
With iOS, I find it extremely fiddly, and with a lot of apps, they are hard to locate. I find the keyboard too small for my hands and there are too many times where it is too easy to select the wrong point on the screen. The positives is that audio is top notch and the camera is good.
Easily, by a long margin for me personally, the best phone is the HTC. Android can do so much more than either iOS or Windows. I like the fact that the home screen has exactly the apps I want to see, where I want to see them. The widgets I use extensively, which add a huge amount of functionality. The downside is for a technophobe, it can be overwhelming. The camera is mediocre too.
My next phone will probably be Android again. I miss the large screen of the HTC when using the iPhone or Nokia and I miss the extra functionality and (for me) ease of use.
I were to choose OS preference, it would be Android, then Windows, then iOS.