Substructured Schwarz methods are interpretations of volume Schwarz methods as algorithms on interface variables. We compare here the Parallel Schwarz Method (PSM, equivalent to RAS) in volume to the new substructured version of PSM in [GH12, p.24] and recently extended to a two-level (i.e. coarse-corrected) framework in [CV22b] and [CV22a], using a geometric and spectral approach for the definition of the coarse space. The expected gain of substructured methods is due to the smaller size of the resulting problems, notably with Krylov-type acceleration techniques when the dimension of the subspace of approximants becomes large [Saa03].