  Average multiplicities and transverse momenta of hadrons are calculated using
a microcanonical hadronization description for a cluster of given total energy
and volume. As a function of the total energy, we determine the critical volume
above which the microcanonical description coincides with the canonical one,
and compare the results with those obtained using one of standard canonical
models. We show that the critical volume depends on the energy and the mass of
the hadrons. For heavy particles, volumes above $50 fm^{3}$ are needed, even
more than$100 fm^{3}$ if one considers transverse momenta. Thus the prediction
of heavy hadron multiplicities in pp, Kp, and $e^{+}e^{-}$ reactions requires a
microcanonical approach, whereas for heavy ion reactions a canonical
calculation is valid. We conclude by showing the importance of the feeding for
the observed hadron multiplicities.
