I know that Netflix supports the iPad VGA cable but does it support the component or composite cable too. If an app like YouTube, Photos or Keynote supports video out does it matter which cable I use. I want to connect my iPad to my HDTV and get the best picture possible for Netflix, Photos, etc.

Not a wired connection but you may be interested in a Apple TV device. I use it to show movies, pics, music from my iPad (and iPhone and iTunes on my PC).