What is the main difference between the BT-200 and the Sony MZ–T2/3?

• The BT-200 has a see-through display, while the Sony MZ–T2/3 is a total absorption type (full and closed) product. With the BT-200, users can see their surroundings while viewing an image on the display.
  
  Sony's product enables individuals to enjoy watching movies and gaming entertainment at home. The BT-200 is a mobile, digital content viewer that can be used virtually anywhere. It's lightweight, portable, and enables users to maintain their view of the external world.