During development, you'll likely spend much of your time testing your iOS app using the iOS Simulator that comes installed with Xcode. While the iOS Simulator is by far the best performing and closest method to running our application on an iOS device, it's still not the same as the real thing. The iOS Simulator uses the computer's CPU and GPU to render the simulated OS, so depending on your development machine, it may end up performing better (or worse) than the actual device.
Thankfully, Expo's ability to test running code on an actual device comes one step closer to the real end product, but there are still differences between a final app and a development app running in Expo. And if you're building a pure React Native app, you won't have the luxury of using Expo to easily run the app on a device...
