  We summarize and extend previous results on the comparison of threshold
resummation, performed, using soft-collinear effective theory (SCET), in the
Becher-Neubert approach, to the standard perturbative QCD formalism based on
factorization and resummation of Mellin moments of partonic cross sections. We
show that the logarithmic accuracy of this SCET result can be extended by half
a logarithmic order, thereby bringing it in full agreement with the standard
QCD result if a suitable choice is made for the soft scale mu_s which
characterizes the SCET result. We provide a master formula relating the two
approaches for other scale choices. We then show that with the Becher-Neubert
scale choice the Landau pole, which in the perturbative QCD approach is usually
removed through power- or exponentially suppressed terms, in the SCET approach
is removed by logarithmically subleading terms which break factorization. Such
terms may become leading for generic choices of parton distributions, and are
always leading when resummation is used far enough from the hadronic threshold.
