  Predictions for our ability to distinguish quark and gluon jets vary by more
than a factor of two between different parton showers. We study this problem
using analytic resummed predictions for the thrust event shape up to NNLL'
using $e^+e^- \to Z \to q \bar q$ and $e^+e^- \to H \to gg$ as proxies for
quark and gluon jets. We account for hadronization effects through a
nonperturbative shape function, and include an estimate of both perturbative
and hadronization uncertainties. In contrast to previous studies, we find
reasonable agreement between our results and predictions from both Pythia and
Herwig parton showers. We find that this is due to a noticeable improvement in
the description of gluon jets in the newest Herwig 7.1 compared to previous
versions.
