Favorite Family Travel Product – Apple iPad, Nintendo DS or Kindle Fire?

When traveling with kids, one of the biggest challenges is keeping them occupied during the many times they’re forced to wait in line throughout the trip.  At the airport, on the plane, checking in at the hotel, at the restaurant, and on and on and on.  Sometimes it’s helpful to let them watch a movie, favorite tv show, or play a game on a handheld device.

Some of the more popular choices are the iPad:

Kindle Fire:

and Nintendo DS:

For us, we do all these things on our iPad.  But with the latest editions of the Kindle Fire HD and Nintendo DS, the choice isn’t so clear.  I’m curious, dear readers, which do you prefer and why?