Resonance Raman excitation profiles and absolute cross sections are presented for three closely related merocyanine dyes as monomers in dichloromethane solution and as H-dimers in dioxane solution. For both monomers and dimers the absorption spectra and the resonance Raman intensities of the 24 to 30 strongest vibrations are quantitatively simulated using time-dependent wave packet propagation methods to determine the geometry changes along each Franck-Condon active mode upon electronic excitation, as well as the homogeneous and inhomogeneous electronic line widths. In addition, an approach previously formulated to describe the vibronic structure of an excitonically coupled homodimer with multiple vibrational modes [Kelley, A. M. J. Chem. Phys. 2003, 119, 3320-3331] is applied to model the dimer spectra. Comparison of these two calculations demonstrates that when the intermonomer coupling is strong the theoretical absorption and resonance Raman spectra of the dimer can be very well approximated by treating the system as a "supermolecule" having a single electronic transition with appropriately resealed vibrational displacements, transition dipole, and electronic zero-zero frequency. The experimental dimer spectra exhibit the reduced Franck-Condon activity expected from distributing the electronic excitation over two monomers. However, deviations in the intensity patterns for individual vibrations suggest additional, more specific effects of dimerization, and the electronic transition moment for the lowest allowed transition of the monomer is not conserved upon dimer formation. An excitonically coupled monomer model therefore appears inadequate to describe the electronic excitations in these strongly coupled noncovalent dimers.