iOS works well when you want solid control over institutionally-owned devices. This generally works best when you play by Apple's rules and buy through them and use Apple School/Business Manager - so if you're going for a BYOD model, this probably isn't the way to do [it]. There is a wide variety of management tools, but bear the costs of each in mind.
Anyone with an iPhone or iPad would benefit from having a macOS-based computer. Additionally, the learning curve for a new user is much less steep than for a Windows computer. Apple has updated its OS for 20+ years, however, still maintains the same basic functionality (turn on/off, open/close apps, etc), the same cannot be said for Windows (Windows Vista, 8, 8.1, 11).
In all likelihood, common users will either already have experience with iOS on their iPhones, or will pick it up quickly. The UI is generally simple and mostly visual. Power users, on the other hand, may feel constrained by the inherent limitations built-in. Root access, terminal commands, and deep customization are not really to be found here.
Lots of help articles online for just about everything under the sun. I have never personally had to engage Apple's support team to comment on their helpfulness.
The software updates have a wide coverage for iPhone models and I love updating software for additional features and/or improved software stability. It has also genuine feel of the phones they offer. Easier to set up and use. It helps me do more productive tasks. If I have the latest phone model, I would have additional software advantages that are already included in my OS.