While a leap from a six-year-old A9 to the same A15 that’s in the iPhone 13 lineup is something nice to think about, I honestly think the storage bump (16GB -> 64GB) is something that will have a bigger impact.
No longer having to be so mindful about what’s on my phone, and how close I am to that 16GB ceiling will probably result in some tangible, day-to-day changes in how I approach pics/video, exploring/installing apps, etc.
I know that sounds silly to all those with 128GB+ iPhones, but when you’ve had just 16GB for over half a decade, you learn to be real tight and careful in what you put/keep in your phone.