For me it’s a few things:

The hardware. I find it more polished. The camera is fast and consistent. The processors are far beyond anything in an android phone. The ecosystem around accessories is just way more built out.

Software fit and finish. Any time I use android the apps and experience just seem a little more janky. iOS is where the money is for dev, and you can tell they put more care into it. Also, I think it is a more predictable platform for developers, so it’s easier to spend time polishing an app. I enjoy photography. The iPhone has a huge ecosystem of great photo apps that interact directly with the built in system photo library. Developers tend to support Apples features and APIs very quick. For example. Apple has Shortcuts, which can be very useful for automating tasks. Android fans will be quick to point out Tasker is similar. The difference is that app developers have embraced Shortcuts and added tons of hook for it. So while Tasker may be technically more capable, in use I haven’t found it to be so.

Apples ecosystem of devices just work together so well. If you use a Mac, iPhone, Apple Watch, AirPods, iPad, AppleTV, and HomePods you get a very nice (not perfect) integrated system.

At the end of the day both are perfectly serviceable. So pick the one that fits your style better. I’ve used both extensively and always find myself coming back to Apple.