We're talking functionality that you routinely see in a website such as questions and answers, providing resources, simple calculations. Such functionality will be easy to implement in a cross platform mobile app.
If you are on a very tight budget, and already have a working web application, re-purposing that within a mobile app may be possible using a web view.
If you are intending to deploy your app to more than just the common Android and Apple devices, cross platform may be a more viable solution.