  Methods able to simultaneously account for both static and dynamic electron
correlations have often been employed, not only to model photochemical events,
but also to provide reference values for vertical transition energies, hence
allowing to benchmark lower-order models. In this category, both CASPT2 and
NEVPT2 are certainly popular, the latter presenting the advantage of not
requiring the application of the empirical
ionization-potential-electron-affinity (IPEA) and level shifts. However, the
actual accuracy of these multiconfigurational approaches is not settled yet. In
this context, to assess the performances of these approaches the present work
relies on highly-accurate ($\pm 0.03$ eV) \emph{aug}-cc-pVTZ vertical
transition energies for 284 excited states of diverse character (174 singlet,
110 triplet, 206 valence, 78 Rydberg, 78 $n \to \pi^*$, 119 $\pi \to \pi^*$,
and 9 double excitations) determined in 35 small- to medium-sized organic
molecules containing from three to six non-hydrogen atoms. The CASPT2
calculations are performed with and without IPEA shift and compared to the
partially-contracted (PC) and strongly-contracted (SC) variants of NEVPT2. We
find that both CASPT2 with IPEA shift and PC-NEVPT2 provide fairly reliable
vertical transition energy estimates, with slight overestimations and mean
absolute errors of $0.11$ and $0.13$ eV, respectively. These values are found
to be rather uniform for the various subgroups of transitions. The present work
completes our previous benchmarks focussed on single-reference wave function
methods (\textit{J.~Chem. Theory Comput.} \textbf{14}, 4360 (2018);
\emph{ibid.}, \textbf{16}, 1711 (2020)), hence allowing for a fair comparison
between various families of electronic structure methods. In particular, we
show that ADC(2), CCSD, and CASPT2 deliver similar accuracies for excited
states with a dominant single-excitation character.
