  It has been known for some time that a hermitian matrix model with a
Penner-like potential yields as its large-N free energy the prepotential of N=2
N_f=2 SU(2) SUSY gauge theory. We give a rigorous proof that a unitary matrix
model with the identical potential also yields the same prepotential, although
the parameter identifications are slightly different. This result has been
anticipated by Itoyama et. al.
