If you want your new app to be more than just a simple view, have polish, have acceptable performance in simple use cases, then it is quite the “yes brainer”. SwiftUI has considerable shortcomings, very real and unfathomable limitations, and many, many performance issues. You might be fooled by how quickly you can come up with a skeleton interface, but that doesn’t make an app. Especially for people who are coming from “React” as many have said here, once they hit those limitations, they would be fish out of water, just like React Native “developers” are dumbfounded what to do once their app doesn’t work as expected, or slows down seemingly inexplicable.
SwiftUI is a nice experiment, but it’s not a serious UI framework, and won’t be for a very long time.
It is a very serious UI framework. People from React (I am not one of them) just understand this better, because they know that the reactive approach is superior for UI. People who have not experienced that have often a problem grasping this simple fact.
SwiftUI has annoying bugs. I haven't hit performance issues yet. But if you encounter these issues you can always escape to UIKit. I already did several times, I have my little set of SwiftUI components already which replace the original ones. For example, Image is a buggy component which doesn't display SVG assets properly. I made an XImage component which fixes that.
On the other hand, doing everything in UIKit from the start is just a waste of developers resources. My time is too precious for that.
Giving my users a good experience is the most important point.
If I give them no experience at all because I cannot get a product of excellent quality done in feasible time would be the worst of all experiences for them.
I am pretty sure given the same amount of time, what you can get done in UIKit will be less and of inferior quality compared to what I will get done with SwiftUI + UIKit where necessary.
SwiftUI is a nice experiment, but it’s not a serious UI framework, and won’t be for a very long time.