The choice of an project template depends entirely on what exactly are you going to develop.
The deference between the standard project and the Telerik project for Silverlight is that the Telerik one is pre-configured to use the Telerik RadControls for Silverlight.
Even if you choose a standard project you could easily convert it to Telerik one in order to use the RadControls. You could read more about create and convert projects here:
As for the Silverlight Business Application you could find more information on the following link:
the Telerik team
Do you want to have your say when we set our development plans? Do you want to know when a feature you care about is added or when a bug fixed? Explore the Telerik Public Issue Tracking
system and vote to affect the priority of the items