I've gone back and forth between iPhones and Android phones. I regularly carry both, but for the last 3 years Android has been my primary phone. But I've used the iPhone X, 7 Plus, and 6 Plus for a solid year each as my primary.
Here are reasons why I think someone might like iOS more...
* iMessage is amazing if you want to be a blue bubble for your iPhone friends. RCS on Android is great, but US phone carriers are still sabotaging the crap out of RCS, so it's roll out is still a mess.
* iOS updates immediately available to all supported phones on day 1. Also easy to enroll in betas if you like to be on the bleeding edge.
* iPhones typically get 5+ years of iOS updates, iPhone 6S from 2015 is running the latest iOS 14 now.
* iOS is very security focused (their business model doesn't revolve around selling ads and customer data).
* If you ever want a smart watch nothing even remotely compares to the Apple Watch.
* Likewise, Apple has a pretty good ecosystem with Watch, TV, iPad, iPhone, and Macbook. Being able to get and make calls with one phone number to your iPhone, iPad, Macbook, etc is really nice.
* iOS cloud backups are much better than Android's backups.
Here are reasons why I think someone might like Android more...
* Choices of phones. Maybe this isn't quite the choice it used to be in some areas. But you can get an Samsung, Pixel, OnePlus, Huawei, Xiaomi, etc. Even if you are on a US carrier and mostly stuck with Samsung, Samsung has a bigger variety of models.
* Expandable stor... Dang-it Samsung!
* UI customization is much better, lots of third party app launchers that significantly change the look and feel of the OS experience to your desires.
* And being able to put your icons where you want and knowing they will always stay there! Stay icons stay!
* I love having access to the file system and easily being able to copy files to and from the phone much easier and share files between apps much easier.
* No ridiculously huge notch. No, you really never get used to a notch the size of the one on iPhones.
* Some apps have more functionality because of less restrictions on Android. For example you can actually buy books in the Android Kindle app.
* Samsung phones integrate pretty well with Windows My Phone app. Not nearly the same level of functionality as iPhones with Macs, but I primarily use Windows so this is more important for me.
I'm probably missing a few other key things for both that are slipping my mind at the moment.