  We elaborate on the dichotomy between the description of the semileptonic
decays of heavy hadrons on the one hand and the semileptonic decays of light
hadrons such as neutron $\beta$ decays on the other hand. For example, almost
without exception the semileptonic decays of heavy baryons are described in
cascade fashion as a sequence of two two-body decays $B_1 \to B_2 + W_{\rm
off-shell}$ and $W_{\rm off-shell} \to \ell + \nu_\ell$ whereas neutron $\beta$
decays are analyzed as true three-body decays $n \to p + e^- +\bar \nu_e$.
Within the cascade approach it is possible to define a set of seven angular
observables for polarized neutron $\beta$ decays as well as the longitudinal,
transverse and normal polarization of the decay electron. We determine the
dependence of the observables on the usual vector and axial vector form
factors. In order to be able to assess the importance of recoil corrections we
expand the rate and the $q^2$ averages of the observables up to NLO and NNLO in
the recoil parameter $\delta=(M_n-M_p)/(M_n+M_p)= 0.689\cdot 10^{-3}$.
Remarkably, we find that the rate and three of the four parity conserving
polarization observables that we analyze are protected from NLO recoil
corrections when the second class current contributions are set to zero.
