React Native and Flutter allow developers to write native mobile apps using one codebase that can target both iOS and Android platforms. This eliminates the need to write separate codebases for each platform, significantly reducing development time and costs compared to developing apps natively for each platform separately. Both frameworks use their own programming languages (JavaScript for React Native and Dart for Flutter) which compile to native code, so apps developed with them can access the full capabilities of each mobile platform like any native app would.

Since one codebase can be shared between platforms, maintaining and updating an app across iOS and Android becomes much simpler compared to managing two completely separate codebases. Any changes or bug fixes only need to be made once in the shared codebase, instead of separately for each native project. This improves sustainability of the codebase over time and reduces maintenance work. It also makes it easier for larger teams to collaborate effectively on a single codebase.

Some key benefits of code-sharing between platforms include:

Faster development cycles – Apps can be developed much more quickly since developers don’t need to redo significant work for the other platform. Common UI components, business logic, and back-end integration only need to be written once. This accelerates the entire development process.

Lower development costs – The shared codebase reduces duplication of effort and allows resources to be utilized more optimally. Fewer resources are required to develop, maintain and update an app on both platforms compared to doing each natively. This significantly lowers overall development costs.

Easier ongoing enhancements – Any new features or functionality only need to be added to the shared codebase rather than to separate codebases. This streamlines the process of ongoing improvements and enhancements to the app over its lifespan.

Simpler collaboration – A single codebase improves collaboration since all developers work on the same code. It’s easier to divide and assign work, integrate changes, and ensure consistency across platforms.

Synced roadmap – New features can be prioritized and planned together for both platforms. The roadmap remains in sync more easily compared to separate native projects.

Agility – Shared code allows leveraging developers’ work across platforms. Resources can be reallocated dynamically based on priorities. It’s also easier to experiment with new features by building them first for one platform.

Another key benefit of cross-platform frameworks like React Native and Flutter is access to large developer communities and abundant third-party libraries/components. Since they are very popular, extensive documentation and support resources exist to help developers with any issues encountered. A rich ecosystem of pre-built open source and commercial modules are also available for common tasks like networking, databases,payments etc. This allows developers to spend more time focusing on their unique app requirements rather than having to rebuild basic functionality.

In terms of user experience, apps developed with cross-platform frameworks can offer near-native performance under normal usage scenarios. While there may still be some differences compared to truly native solutions, the gap has reduced significantly in recent years as these frameworks have matured. User interfaces built with React Native and Flutter can be highly responsive, animated and customized to follow each platform’s native look and feel. This provides a great mobile experience for users without compromising too much on native integration.

In terms of long term flexibility also, these shared codebases can adapt to changes in either mobile platform more conveniently. Any API additions or modifications made by Apple/Google to their respective SDKs would need only localized changes in the cross-platform codebase, rather than overhauling separate native projects. This makes the app codebase more future-proof and resilient to platform changes over its lifetime.

To conclude, React Native and Flutter offer compelling benefits for developing high-quality cross-platform mobile apps. Their shared codebases significantly increase development speed and reduce costs compared to native solutions. Large and active developer communities further strengthen these frameworks. While each tool has its own pros and cons, they both allow building apps that deliver close to native user experiences on iOS and Android using a single codebase – improving productivity, sustainability and overall efficiency for mobile development teams.