  For the past decade, SALT2 has been the most common model used to fit Type Ia
supernova (SN Ia) light curves for dark energy analyses. Recently, the SALT3
model was released, which upgraded a number of model features but has not yet
been used for measurements of dark energy. Here, we evaluate the impact of
switching from SALT2 to SALT3 for a SN cosmology analysis. We train SALT2 and
SALT3 on an identical training sample of 1083 well-calibrated Type Ia
supernovae, ensuring that any differences found come from the underlying model
framework. We publicly release the results of this training (the SALT
"surfaces"). We then run a cosmology analysis on the public Dark Energy Survey
3-Year Supernova data sample (DES-SN3YR), and on realistic simulations of those
data. We provide the first estimate of the SN+CMB systematic uncertainty
arising from the choice of SALT model framework (i.e. SALT2 versus SALT3),
$\Delta w = +0.001 \pm 0.005$ -- a negligible effect at the current level of
dark energy analyses. We also find that the updated surfaces are less sensitive
to photometric calibration uncertainties than previous SALT2 surfaces, with the
average spectral energy density dispersion reduced by a factor of two over
optical wavelengths. This offers an opportunity to reduce the contribution of
calibration errors to SN cosmology uncertainty budgets.
