Depends what you are looking for.
The concepts are different:
https://medium.com/swift-blondie/swiftui-vs-react-native-84b4e2103429
React has a longer existence than SwiftUI, so it is probably more developed (there are still many things missing in SwiftUI). And it allows for multi platform development (its main interest). But it misses some important capabilities.
But in the longer run, SwiftUI will likely be faster to cope with the evolutions of iOS.
If you are not looking for multi platform, I would clearly recommend SwiftUI. But that's just a personal opinion, not the result of any benchmark.