Are you serious? If the EM drive works we are at the gates of a major revolution in Physics (as in 'our understanding of Physics'). First we should have to understand how it works, tinker with it till the smallest-lightest-efficientest designs emerge. In parallel, other people would be trying to determine WHY it works. That's a much bigger task, that requires a rewriting of most Physic's textbooks. When we have a new theory that explains the EM drive, then probably still better drives can be designed, perhaps using other kinds of radiation.
What I'm driving at, is that discussing how possibly adequate or inadequate this EM drive is to space travel is like discussing the usefulness of electricity when good old Thales started rubbing amber pieces against animal skins.