  We compare, in an extensive and systematic way, linear theory results
obtained with the hybrid (ion-kinetic and electron-fluid), the gyrokinetic and
the fully-kinetic plasma models. We present a test case with parameters that
are relevant for solar wind turbulence at small scales, which is a topic now
recognized to need a kinetic treatment, to a certain extent. We comment on the
comparison of low-frequency single modes (Alfv\'{e}n/ion-cyclotron,
ion-acoustic, and fast modes) for a wide range of propagation angles, and on
the overall spectral properties of the linear operators, for
quasi-perpendicular propagation. The methodology and the results presented in
this paper will be valuable when choosing which model should be used in regimes
where the assumptions of each model are not trivially satisfied.
