I'd always use a screen protector for an iPhone or tablet. The screen is the main user interface and you don't want an annoying scratch you know will stay until you get your next phone or replace the screen because of a fatal drop. Also if you plan to sell your iPhone or iPad, having a flawless screen will boost your selling price by 30-40%. As a bonus, having a matte screen protector on the iPad Pro that simulates paper when using the Apple pencil increases the value of using a screen protector by a lot! My special tip.
