The Times' Dennis Overbye reports that the two scopes each have a 94-inch primary mirror, just like Hubble. That's twice the size of the planned mirror for Wfirst, so it would have four times the light-gathering ability. Also, they have a shorter focal length, giving them a wider field of view in which to look for phenomena like supernovae. They're "Stubby Hubbles," according to Matt Mountain, director of the Space Telescope Science Institute, which manages the Hubble. He also told Overbye, "They were clearly designed to look down."