  Many numerical techniques for the description of quantum systems that are
coupled to a continuous bath require the discretization of the latter. To this
end, a wealth of methods has been developed in the literature, which we
classify as (i) direct discretization, (ii) orthogonal polynomial, and (iii)
numerical optimization strategies. We recapitulate strategies (i) and (ii) to
clarify their relation. For quadratic Hamiltonians, we show that (ii) is the
best strategy in the sense that it gives the numerically exact time evolution
up to a maximum time $t_\text{max}$, for which we give a simple expression. For
non-quadratic Hamiltonians, we show that no such best strategy exists. We
present numerical examples relevant to open quantum systems and strongly
correlated systems, as treated by dynamical mean-field theory (DMFT).
