Short answer: iOS, of course.
Long answer: Apple is a giant-capitalized company that pits itself against a huge zoo of android devices. She divides the world of gadgets into Apple and not Apple. Let's be realistic: this is not explainable by marketing alone, and stems from the quality of these devices.
The iOs system has an amazing level of security, it cannot be hacked by the best intelligence services in the world.
Optimization. Work speed. Already very old devices like the iPhone 5s still receive the latest updates and work great. New ones just fly.
Laconic design with the most convenient usability. Consistency: all application icons and applications themselves are designed in almost the same style, corresponding to the style of the entire system. Good style. I look at the iOS desktop and see the integrity. I look in Android and see a zoo of icons from bearable to completely ugly. The same thing happens inside applications. At the same time, devices from google with "naked" android look more or less tolerable, other manufacturers definitely want to make their own firmware of varying degrees of ugliness and lagubility.
App quality: strict store moderation, minimal garbage, a large number of exclusives, constant collections with recommendations.
The last point stems in part from developer convenience. Swift is an excellent programming language developed by Apple itself. objective-c is not much worse. Both are incomparable to java.
The main criterion is how interested the user is in optimizing the use of his mobile phone. Wants everything to work out of the box - iOS. Likes to change launchers (in an advanced version - to get administrator rights, install alternative firmware) - Android.
Although, of course, you can just buy the latest Android flagship: it will do exactly the same as the iPhone, but much cheaper :-)
Everyone is spying on each other, and, relatively speaking, three years ago, grouping of notifications by applications appeared in Android, and recently at the Apple conference it was announced for iOS.
There are a lot of features in both systems that you can use to make a funny meme by making a list of these features and writing: Thank you, Apple, you gave us 2013 back. Because all these features were in Android in 2013. Or, on the contrary, write: Thank you, Google, you returned 2012 to us, because all these functions were in iOS.
It seems to me that it is more correct to consider not just systems in isolation from devices, but systems and iron together. Apple's strong point is its very low fragmentation - 81% of its mobile devices have the latest version of iOS 11. In the Android camp, only 6% of devices have the latest version. This, of course, causes difficulties in terms of supporting these systems, not all devices receive updates at the same time.
Besides, there are many manufacturers of Android phones. Therefore, it sometimes happens that the hardware is not so well optimized for the work of software. At the same time, there are wonderful flagships on Android.
Recently, people are choosing not a single phone, but an ecosystem. If a person wants to build his habits around the Apple ecosystem (he has a McBook, he has an Apple Watch, an Apple TV), it is clear that he will make a choice in favor of iOS. If a person is closer to PC and Google services, he should choose Android.
It all depends on your personal preference.
Someone prefers Android , someone iOS (like me: D).
If you are interested in an open file system and the ability to customize the interface, then choose Android.
If you prefer regular updates and OS security, then choose iOS