For years, I preferred Android over iPhone, usually citing its customizability and availability from a large number of manufacturers. This stands in stark contrast to iPhone, which has notably fewer customization options than Android and is only made by Apple. IPhone has no homescreen widgets; non-App Store apps are very difficult to install; it has no centralized storage; and the list goes on. There is one area in which iPhone continues to outshine Android though: security.
Because Apple makes their own devices and designs their own bespoke operating system (iOS) to work more or less seamlessly with their hardware, they have total control over critical security and system updates. When they detect or are informed of a serious flaw in their software, they can push out an update to all Apple devices at once.
This stands in stark contrast to Android. When the iPhone was released and took the world by storm, Google knew the only way they could compete was to adopt the opposite strategy from Apple, namely, making Android's operating system free, open source, and completely customizable by the various manufacturers. That's why iPhones are always iPhones, but Android phones vary wildly in design, features, internals, and software. A phone manufactured by Samsung looks and acts very differently from a phone designed by Lenovo, even though they are both running Android.