If you are unclear of the value of a mobile app and how people will use it, choosing to build a mobile website first may be the best course of action. With this method you can test whether or not your product has a market fit before spending the time and money on developing a native application.

There are plenty of situations where native is clearly the right choice from the beginning. Native apps are necessary when taking advantage of uniquely mobile capabilities such as a functional offline product and having a strong in-app purchase flow.