Another advantage to the above-ground shelters - it'd be a heck of a lot easier for a handicapped person to get into one of those rooms than to go down steep and narrow steps into a pit. Be a lot easier too to herd the family pets quickly through a door into a room, especially if you have multiple panicked pets and a tornado is bearing down on your neighborhood.
But I like the idea of an in-ground shelter, if for no other reason than it'd be handy for working on the underside of your car
Good points. I think I prefer the in ground, but it would be nice to know the real-world survivability of the safe-room type setups in the worst case scenario.