Well, my vote would definitely go to iOS. There are a couple of reasons for this.
1. iOS has a minimalistic and simple look to it. There is a notification custom center that manages all your notifications. The interface is quite user friendly.
Windows has the same look as on a Windows PC.
2. The quality of apps you get on iOS are is unquestionable. The stringent quality measures being employed by Apple reduce the number of malware and fake apps. Besides it does not allow you to download apps from any third party app store. Windows OS has considerably less number of apps. There is a little chance of getting your favourite app. The Windows store has around 17000 apps while iOS boasts of around 1.2 million.
3. In terms of flexibility, however, Windows appears a bit better placed. The iOS is quite rigid. Windows allows you run any desktop app on it and connects to a wide range of devices and peripherals.
Live....and Let Live!