  We show that different stellar-mass estimation methods yield overall mass
scales that disagree by factors up to ~2 for the z=0 galaxy population, and
more importantly, relative mass scales that sometimes disagree by factors >~3
between distinct classes of galaxies (spiral/irregular types, classical E/S0s,
and E/S0s whose colors reflect recent star formation). This comparison
considers stellar mass estimates based on (a) two different calibrations of the
correlation between K-band mass-to-light ratio and B-R color (Bell et al.,
Portinari et al.) and (b) detailed fitting of UBRJHK photometry and optical
spectrophotometry using two different population synthesis models
(Bruzual-Charlot, Maraston), with the same initial mass function in all cases.
We also compare stellar+gas masses with dynamical masses. This analysis offers
only weak arguments for preferring a particular stellar-mass estimation method,
given the plausibility of real variations in dynamical properties and dark
matter content. These results help to calibrate the systematic uncertainties
inherent in mass-based evolutionary studies of galaxies, including comparisons
of low and high redshift galaxies.
