I think the issue is that if the vertically-folding EEZZ/Qix frame hinge is accidentally left opened, the bike is still still rideable whereas a Brompton, Dahon/Tern will be nearly impossible to ride because the the frame would buckle out to the side providing a visual reminder to close the hinge. So theoretically, the EEZZ/Qix hinge design could be more dangerous for those who forget to close their hinges. One could imagine that the EEZZ/Qix could suddenly fold while riding if the bike were to be ridden with the hinge still open and the front brake applied.

Bottom line, don't forget to close your hinges.