ios 10.3.1 isnt just any os update its an apple os AND fs update

ios 10.3.1 isnt just any os update its an apple os AND fs update yes as well as updating your devices OS it will also update your devices filesystem (from HFS+ to AFS)

• http://uk.businessinsider.com/apple-ios-103-update-iphone-historic-2017-3

so you might find it slower than a regular update

• http://appleinsider.com/articles/17/03/27/lengthy-ios-103-install-time-likely-due-to-conversion-to-new-apple-file-system

PS fed up with all those mobile updates then dont worry mobiles will die

• http://uk.businessinsider.com/death-of-the-smartphone-and-what-comes-after-2017-3