Is Inelastic Neutron Scattering (INS) any good compared to synchrotron IXS for determining phonon dispersion relations?

Both INS and IXS can be used to study phonon dispersion relations. While INS requires large sample size due to low inelastic scattering cross section, IXS using synchrotron x-ray sources do not require a small sample as extremely intense synchrotron x-rays can be incident on small sample area. Therefore, is INS any good now to study phonon dispersion relations, or is it obsolete since synchrotron sources have come?

However, the large absorption cross section also means that, with x-rays, radiation damage can be a serious issue, even with the relatively (as compared to other synchrotron work) weak meV-bandwidth beams used for IXS: protein crystals and polymers show visible damage on the hour time scales of typical scans, and the author has observed changes in elastic intensities in IXS spectra on these time scales. (Note, the trick of freezing a sample as used in structural studies is of arguable efficacy for IXS, as, in principle, the dynamics can change as soon as particles are ionized). As the relationship of the isotopic species and neutron scattering cross-section is complex, as opposed to the $$\sim Z^2$$ scaling for x-ray scattering, there also can be advantages for each (x-rays or neutrons) depending on the atoms/isotopes in the sample. However, the x-ray analogue of isotope replacement in INS, which is tuning to atomic resonances to change cross-sections to help identify features of the scattering related to particular atomic species, is not yet possible with meV resolution (see the section on RIXS, below)