If you are developing an app, you should not only use the simulator but also a real device. But what is the best test device at development time?
Simulator vs. Real Device
As I pointed out in my “Simulator vs Real Device” article, it is not a good idea to use just the simulator at development time: The simulator has some advantages like faster deployment and a better access to the file system. However, it tells you nothing about the performance of the app. So it is very advisable to use not only the simulator but also a real device.
But what device should you use? Imagine you are developing an iPhone application that targets iOS 9. Should you just use your new iPhone 6S? No, that’s not a good idea! Instead you should use both the oldest and newest devices that you have.
The Oldest Device
The oldest supported device gives you the best information about the performance of your app. The oldest device has the slowest CPU and GPU, so if the app performs well on this device, it will perform even better on all newer devices. If you are using just the newest device at development time, it is very likely that you will run in performance issues on older devices.
However, if your app has some features that need a lot of performance, it is sometimes not avoidable to make some performance compromises on older devices.
The Newest Device
Although it is very advisable to use an old device at development time, you should use the newest device that you have as well. The reason for that is that newer devices have more features. For example, the iPhone 6S supports 3D touch and older devices doesn’t. It is not testable on the simulator so that this device is the only way to support these features.
But this doesn’t mean that you have to buy always the newest device. If you are not supporting the newest features that are specific for this device, you don’t need to buy it.
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