I tried to go to iOS just for curiosity since 2 years but I think the next device will be an Android again for these reason:
- you cannot simply install applications outside the AppStore
- developing applications even for personal use requires macOS, an Apple developer account, etc
- it lacks of decent applications, such as an email client that works, thanks to limitations imposed by Apple on what the applications can do in background
- it comes with stupid limitations. Such as you can't to a software update on a mobile network (why? To this day with cheap plans that gives you 50G or even unlimited data for 10 euros at month a lot of people no longer even have a landline internet connection and thus Wi-Fi at home, and have to use another phone in hotspot mode to download an update, this is pure insanity of Apple!)
- it works well if you are all-in in the Apple ecosystem, for example you have also a Mac, but it doesn't integrate with Windows (the Windows phone companion that lets you to receive notifications on the PC and other stuff is only available for Android, since iOS doesn't have APIs to do that stuff such as read notifications).
- the only browser allowed is basically Safari and this to me is very wrong for the open web (it's true that in Android you have Chrome, but you can install whatever browser you want, such as Firefox). Safari doesn't support progressive web apps for example for no reason, so you are forced to install an app while you could have used its PWA enabled website.
- you are forced to use Apple services, while in Android using Google services is an option (you can have an Android OS without Google Apps, even if it can be impractical I like having this possibility at least in theory). For example the only way that I found to backup my photos was to pay iCloud, since Google Photos (that did give you unlimited space back then) didn't work in background and thus you have to open it to sync (something that is pretty useless for a backup tool that you want to be always running...)
- it's less user friendly, there are things that are complicated for no reason. This was confirmed by a lot of people that transitioned to iOS and find it more difficult to use
- to this day it's practically impossible to mod (jailbreak) an iPhone to overcome its limitations. In the past there was jailbreak that really did solve many of the issues, but this day it's nearly impossible
- lack of support for open standards, such as the usage of the proprietary lightning connector instead of USB-C (something that is now a requirement in the European union by the way)
From the hardware perspective, it's well built for sure, but I find it too expensive for what it offers. The iPhone that I actually have (an iPhone XS bought new for 600 euros) it seemed expensive when I bought, now to get an iPhone of a similar range (that is an iPhone Pro) you have to spend at least than double that price! A decent Android that is enough to me for my daily tasks can be bought for 200 euros, a top spec one for 600. To me the added cost of an iPhone is not justified.