The difference is, in SwiftUI you fire up Xcode and you are up and ready to build the thing you intend to. No tooling setup, no intermediate steps to transpile the code into something you can’t recognize and the “backend” that deals with the logic is the same language with the same paradigms. Mind you, SwiftUI is considered a downgrade when it comes to tooling. Yet everything fits and you didn’t spend mental energy to try to make the tools work as intended.
My mantra now is to use the tool that is built to do the things I want to do and stop trying to make make it work in ways it’s not intended to. That’s why when I want to have a web interface I simply work with DOM directly. That’s how the creators of the web browser intended:) No virtual DOM, no libraries doing magic and managing the DOM for me. I'm sure there's place for ReactJS too, it's just that its not for most use cases.
All I want is tools that I can fully fit in my working memory and don’t spend time trying to make things work so I can do the work I care about. Simplicity and robustness is the paramount.