Windows has an option to turn on or off auto updates. IOS will auto download os updates and take up space, not letting the user get that space back unless they update.
Windows has a list of system requirements on the box. IOS will auto download large os updates even if you don't want them and doesn't tell you before downloading how much space it will take.
Windows let's you downgrade os versions if you don't like the update. IOS doesn't.
The fact that apple forces the updates to download is the only real problem with this I have. It really irritates me that they can hold some of your space hostage until you update. As for the space the installed OS takes. Every computing device since computers came to consumers advertises the size of the whole drive regardless of how much the OS takes up. If consumers are to stupid to do a little research into their real device needs before they buy, then it's their fault, not Apples.