  We compare the structures of model atmospheres and synthetic spectra
calculated using different line lists for TiO and water vapor. We discuss the
effects of different line list combinations on the model strutures and spectra
for both dwarf and giant stars. It is shown that recent improvements result in
significantly improved spectra, in particular in the optical where TiO bands
are important. The water vapor dominated near-IR region remains problematic as
the current water line lists do not yet completely reproduce the shapes of the
observed spectra. We find that the AMES TiO list provides more opacity in most
bands and that the new, smaller oscillator strengths lead to systematically
cooler temperatures for early type M dwarfs than previous models. These effects
combine and will help to siginificantly improve the fits of models to
observations in the optical as well as result in improved synthetic photometry
of M stars. We show that the Davis 1986 \fel-values for the $\delta$ and $\phi$
bands of TiO best reproduce the observed (V-I) color indices.
