Two things prevent me from switching to iPhone:
1) Notifications are a mess - Android does it so much more intuitively. I use a Pixel for my personal device and an iPhone for work, and I'm constantly missing notifications on the iPhone. Apple's system is frankly rubbish.
2) Having to keep an app open to background download. For example, I use Dropbox / Google Photos to upload pictures taken. However, on the iPhone I have to keep the app open and screen on for each app to fully upload pics - what a faff. Plus, it negates the point of camera upload, as I want the pics uploaded to the cloud just in case my phone gets lost/stolen. So I have to remember to launch each app periodically. On any Android phone it just happens in the background.
If Apple fix the above, I'd seriously considering moving my personal device to an iPhone. People have asked for a better notification system from Apple for years, so I'm not holding my breath.