The wide field imaging capability of WFIRST enables large area surveys at a much faster rate but at the same resolution as HST/WFC3/IR. The HST/WFC3/IR PHAT Survey required 432 pointings to cover M31 while only 2 WFIRST pointings are required.
WFIRST, the Wide Field InfraRed Survey Telescope, is a NASA observatory designed to settle essential questions in the areas of dark energy, exoplanets, and infrared astrophysics. The telescope has a primary mirror that is 2.4 meters in diameter (7.9 feet), and is the same size as the Hubble Space Telescope's primary mirror. WFIRST will have two instruments, the Wide Field Instrument, and the Coronagraph Instrument.
The Wide Field Instrument will have a field of view that is 100 times greater than the Hubble infrared instrument, capturing more of the sky with less observing time. As the primary instrument, the Wide Field Instrument will measure light from a billion galaxies over the course of the mission lifetime. It will perform a microlensing survey of the inner Milky Way to find ~2,600 exoplanets. The Coronagraph Instrument will perform high contrast imaging and spectroscopy of individual nearby exoplanets.
WFIRST is designed for a 5 year mission, and will launch on an Evolved Expendable Launch Vehicle (EELV) out of Cape Canaveral.