Advertising can  use either app or wap. The difference between a mobile app and a browser is that when you use a browser, you can move from one web site to another. However, if an app can have short-cut links to switch apps, then there is no difference. The difference between them blurs. The browser experience will become app like and the app will provide the convenience of a browser.

To an advertiser, what matter is the audience. The way to reach it could be an app or web or social, search or display. That is not so important. Whatever works for the target audience is adopted. The medium is not more important than the consumer. In the beginning, native apps were favoured, as the browsers were slow. However, browsers are more powerful now.