The need for a TabBar, NavBar, or Window based application is mostly subjective. This will depend on:
- How you want the application to look
- Whether or not you need the functionality of the nav and tab bars
Window only applications are typically the EASIEST to implement, at first, but do not provide the necessary functionality that many people are use to. Window/OpenGL based applications are ideal for games that require "full screen."
TabBar applications are perfect for applications that have several main "sections." Akin to a website that has "blog", "products", and "contact us", you can have many sections with the TabBar.
NavBar applications let you stack up additional views, one at a time, that you can transition to as necessary. A typical implementation of this is a "drill-down" menu.
Good luck!
-Kevin