The Flux-Reversal (FRPM) machine is a kind of stator-PM machine in which the PMs with different polarities are located on the surface of each stator pole, the armature winding generally adopts the concentrated winding arrangement, and the rotor is simply iron core with salient poles. The FRPM machine exhibits bipolar PM flux linkage because the flux linkage with each armature coil reverses polarity as the rotor rotates.
The higher the number of PMs used per stator pole, the higher the number of rotor poles and hence the lower the rotor speed are resulted.
The Vernier (VPM) machine with PMs located in the stator is commonly termed the vernier hybrid machine. This stator-PM VPM machine operates in a similar manner to the rotor-PM VPM machine (and this one is I would say more common). The configuration of this VPM machine is very similar to that of the flux-reversal PM machine in which the armature winding is wound on the stator iron protrusions facing the slotted rotor, and all PMs are mounted on the faces of those iron protrusions.
In fact, depending on the type of Vernier machine you are looking at, it might just as well be the same thing. The equation of gearing is different between rotor- and stator-PM VPM, but the equation is the same between stator-PM VPM and FRPM.