A recently developed strategy for utilizing surface-enhanced Raman scattering (SERS) to obtain uniquely detailed vibrational information for a myriad of organic land other) adsorbates on transition metals in electrochemical and other ambient environments is illustrated for benzene and a pair of monosubstituted benzenes, toluene and benzonitrile, on palladium and rhodium films in aqueous solution. The transition-metal layers, formed by constant-current deposition onto SERS-active gold substrates, can be sufficiently thin (3-5 monolayers, ML) so to yield near-optimal Raman scattering intensities, yet are essentially devoid of exposed "pinhole" sites, thereby eliminating spectral interferences from adsorption onto gold. Benzene was selected in view of the detailed vibrational information also available for this archetypical organic chemisorbate on transition metals in ultrahigh vacuum (UHV) by means of electron energy loss spectroscopy (EELS). Comparison of the spectral information obtained by SERS and EELS provides an instructive assessment of how the different properties, including surface-selection rules, characterizing these related energy-loss spectroscopic methods influence the vibrational information content. The "dynamic polarizability" surface-selection rules followed by SERS enable most adsorbate normal modes to readily be detected and identified, aided by H/D isotopic substitution, even for such flat oriented adsorbates. The relative Raman band intensities combined with adsorption-induced frequency shifts also provide a reliable guide to chemisorbate structure and surface bonding. These SERS characteristics compare favorably with corresponding EELS data : while both techniques provide detailed vibrational information for "flat" oriented aromatic molecules, the former method allows at least as complete a spectroscopic analysis to be undertaken, yet is uniquely applicable to transition metal-nonvacuum interfaces. Toluene chemisorption on palladium yields rich SER spectra that also signal a "flat" aromatic orientation via metal ring pi interactions, again similar to the bonding deduced by EELS at related metal-UHV interfaces. Benzonitrile, however, yields markedly different SER spectral features compared with toluene that are indicative of chemisorption primarily via the nitrile substituent rather than the aromatic ring. This binding geometry contrasts the flat adsorbate orientation deduced by EELS on copper and gold. The difference is probably due to the influence of solvent (and possibly also interfacial charge) in the electrochemical environment. While the SERS band intensities are attenuated progressively for increasing transition-metal thickness, this "overlayer-film" strategy is viable even for markedly thicker (similar to 5-10 nm) layers. The likely broad-based utility of the approach for in-situ surface vibrational characterization of such catalytically significant interfaces is considered in light of these findings.