When Google released the Android app for Google Docs, the application didn't include many features that weren't available from the browser. The latest updates made the app more useful: there's a better tablet interface, offline access to your documents and now you can edit documents collaboratively.
The most powerful Google Docs feature (real-time collaboration) is now available on Android devices and you don't have to switch to the desktop interface. You can see the changes in real-time and all you edits are saved almost instantly. While the Android editor lacks many features that are available in the desktop version, you can use rich text formatting: bold the text, change the color, create lists, indent paragraphs, undo and redo the changes.
"We've brought the collaborative experience from Google Docs on the desktop to your Android device. You'll see updates in real time as others type on their computers, tablets and phones, and you can just tap the document to join in. We also updated the interface to make it easier to work with your documents on the go. For example, you can pinch to zoom and focus on a specific paragraph or see the whole document at a glance," informs Google.
Suddenly, the mobile web app pales when compared to the native app and that's probably the reason why the Google Docs mobile site promotes the app every time you go there.