  We present a comprehensive numerical study of dynamical mass generation for
unquenched QED in four dimensions, in the absence of four-fermion interactions,
using the Dyson--Schwinger approach. We begin with an overview of previous
investigations of criticality in the quenched approximation. To this we add an
analysis using a new fermion-antifermion-boson interaction ansatz, the
Kizilersu-Pennington (KP) vertex, developed for an unquenched treatment. After
surveying criticality in previous unquenched studies, we investigate the
performance of the KP vertex in dynamical mass generation using a renormalized
fully unquenched system of equations.
  This we compare with the results for two hybrid vertices incorporating the
Curtis--Pennington vertex in the fermion equation. We conclude that the KP
vertex is as yet incomplete, and its relative gauge-variance is due to its lack
of massive transverse components in its design.
