TL;DR: Native Java code is still better than NativeScript or React.

It largely depends on your application requirements as well as business requirements. If you want cross platform app developed quickly and you are low on engineering resources, React or Native might seem more appealing.

However, once you are deep into the app, you'll want to write in native java. Sometimes there are problems with 3rd party integrations and the generated app and once a bug is on your production app in Play Store, it might will be mighty difficult to get most of your existing users to update to the new version. Since this isn't web, even the updates you submit to Play Store reflect after a day.

If you are worried about having a cross platform app, then you might want to try building a responsive web app which caters to almost any smartdevice.

I will agree with @Sidhant and @Dhayanandhan on the front that React offers a faster realisation to end product and doesn't skimp on performance at the same time - (over solutions like PhoneGap and sorts )

But there comes a time when pin pointing stuff requires a dive into java .

But React in particular is maturing well enough by the moment and might just be a viable solution for production ready code

Pure Native Code will always be faster than other alternatives such as ReactNative or NativeScript.

As far as I know facebook is pushing their boundaries to make ReactNative as fast as possible.

facebook.github.io/react-native/docs/performance.…

It looks awesome and developer experience is great. It needs some time to mature. I think it is fairly fine for many types of Apps.

Cross-platform apps face a crucial choice in their development planning phase – should the application be developed as a native app, or should it be developed as a hybrid or web-based application? This question used to impact the amount of work to be done – namely, until recently, choosing to pursue a native approach for your application meant consigning your development team to simultaneously developing functionality in Objective C/Swift (for iOS) or Java (for Android). However, this is no longer a consideration when it comes to creating a native app experience. Below we’ll look at using JavaScript to create a cross-platform native app experience by examining React Native and the combination of AngularJS 2 and NativeScript. We’ll look at what each has to offer, then compare the two to provide a heuristic for making the right choice for your application. You can get it from (Citra 3DS Emulator)[iappsbuzz.com/citra-3ds-emulator].