iOS attracts with its security (no need to download antivirus software), visual aesthetics and convenience. Have you ever heard a virus hit your iPhone ?! I, personally, do not know. I only know that it was only recently that a virus hit MacOS for the first time. But that's another story.
Online privacy is a concern for many. Here, everyone decides for himself: to trust the giant Google or Apple with their data. I, personally, am more inclined towards Apple (reputation and status of the company), since there are only scandals with Google: either the data was leaked there, then they are following you from the front-end ...
On Android, for example, more opportunities for developers of applications, games; but, at the same time, it is an open system, and iOS is not.
On Android you can live without Google Play, but on iOS without the App Store - no (although some of them use undermines, throwing off programs through iTunes)
In general, everyone decides for himself based on his tastes and needs from the device.
In such matters, you need to focus on your own needs and the size of the wallet.
If you need reliability, security, high optimization and long-term support, then your choice is iOS.
If Openness and customization are important to you, then the choice should fall on android. And then you have to look at the circumstances and means.
I see no reason to breed another holivar here, everyone already knows the strengths and weaknesses of these platforms. And the question itself seems strange, 2018 is in the yard, not 2010.