Let me just say that I don't pledge my allegiance to a specific brand or company. I started with an iPhone 3g, moved to a Galaxy S4, back to iPhone, back to OnePlus, and now back to iPhone.
My biggest gripes come from moving from a "stock" android experience on the OnePlus 3T, back to the restrictive ecosystem that is Apple. Hardware-wise, the X is a monster. Though the more I use it and its old, familiar software, I miss the customization and the small things.
The company I work for was built on Google's enterprise backbone. So like i said, I miss the small things. When signing in to google on Android, it will automatically authenticate because it knows your device. Whereas on the iPhone, you're prompted to open the Google app and click a button. Yes it works fine, but it's not as seamless. Other things like known safe areas, YouTube/Gmail/Maps optimizations, and Google Home integration make me miss it a lot.
I love how things just work with Apple, be it the watch, AirPods, etc, but the phone never feels like it's mine. If that makes sense. I can change the wallpaper and app layout, but that's about it.
And the notification system is a dumpster fire right now. Always has been though.