  Calculations for mean field dynamo models (in both full spheres and spherical
shells), with both algebraic and dynamic $\alpha$--quenchings, show qualitative
as well as quantitative differences and similarities in the dynamical behaviour
of these models. We summarise and enhance recent results with extra examples.
  Overall, the effect of using a dynamic $\alpha$ appears to be complicated and
is affected by the region of parameter space examined.
