One of the things I’ve noticed as the user of both an older and a newer iPhone is that the 4.7″ screen that is on the iPhone 6/7/8 is now the baseline standard being used for iOS design decisions.
In iOS 11 Apple have made a number of design decisions that increase the amount of screen being used by items.
In the AppStore, as an example, the icons have got bigger and the titles have got bigger, so that the number of apps you see in the Update section have reduced and the titles are often truncated on a 4″ iPhone 5/5S:
Another example of the design choices being made is the lock screen and associated notifications. If you have a clock on your lock screen and you are playing some audio then notifications are almost useless because you only get part of the first notification without scrolling:
Screen design decisions are a balance between content and white-space, white-space is the space between the content. Good design is defined by the white-space more than the content. That’s where the iOS 11 design decisions are being driven from, as screens have got bigger on the iPhone 6/7/8 (4.7″) and the 6/7/9 Plus (5.5″) Apple are increasing the amount of white-space so that the design stays good on those devices.
Anyone who has used a corporate application will know how awful it is when white-space is ignored and content is crammed on to screens. Apple could have used the extra screen space on the newer iPhone models to squeeze in more content, which I’m sure they’ve done, but they’ve balanced it with an increase in white-space. Those design decisions mean that the content on the 4″ screen feels like it’s a bit too spaced out.