RCDefaultApp is a panel that allows the user to choose the default application used for various combinations of URL, file extensions, file types, MIME type ...
You should know that MacOSX uses extensions and settings for each file type to open an application from Finder. While Safari and other applications using the settings file types URLs and MIME.
RCDefaultApp setting also allows for the use applications that match digital cameras or FireWire.
All these functions can be adjustable with Finder's Get Info panel, but not as intuitive and accessible as RCDefaultApp.
