Bento galore at Shinagawa station

What is the hottest item for people getting ready to hop on Shinkansen?  Bento or Ekiben is the most popular item to buy before getting on board because it makes the long train ride much more enjoyable.  Shinagawa station has a plethora of bento vendors which makes choosing one extremely difficult.  Paolo shares pointers on how to choose some of the best bentos.