- hardware Secure Enclave (as time of writing, only Samsung devices and latest Google Nexus also have a similar hardware, as far as I know)
- strong sandboxing (again, only Samsung devices with Knox can really compare)
- restrictions on which apps you can get, that filters on malicious apps (ex: fake gmail app). It is void if you use jailbroken iOS or allow sideloading on Android.
- security updates are both more frequent (except Google devices, all Android manufacturers always lag behind for updates), and available to older devices (varies from manufacturer to manufacturer, but it's generally way less than Apple)
Of course, you need to factor in the delay to respond to security flaws (I don't have that kind of data), and other factors too, as well as decide if iOS suits you. That's for you to decide.