Biggest advantage for native apps is higher speed, read this for instance:
In addition, not all native (advanced) features are availible to webapps.
Another reason for choosing native apps is that it will get some free promotion from the Google Play/App store. If you build an webapp youll need to do your own advertising. The advertising itself will be easier for a webapp however and with the large amount of applications in the app stores your native app will most likely get only a slight attention the first day when it appears in the 'new apps' category.
There are pros and cons for each, ultimately you might just want to write 3/4 apps: webapp, android and ios (and perhaps windows)
This depends on the succes of your app.