Particle-laden flow in a vertical channel was simulated using a Reynolds-averaged Navier-Stokes two-fluid model including a Reynolds-stress model (RSM). Two sets of cases varying the overall mass loading were done using particle sizes corresponding to either a large or small Stokes number. Primary and turbulent statistics extracted from counterpart Eulerian-Lagrangian and Eulerian-Eulerian anisotropic-Gaussian simulations were used to inform parameters and closures applied in the RSM. While the behavior at the center of the channel compared well with the other simulations, including the transition from fully developed turbulent flow to relaminarization to cluster-induced turbulence as the mass loading increased, the behavior close to the wall deviated significantly. The primary contributor to this difference was the application of a uniform drag coefficient, which resulted in the RSM overpredicting the fluid-phase turbulent kinetic energy close to the wall. When considering small Stokes particles, the RSM at greater mass loadings reproduced the transient clustering observed in the other models. This was not observed using larger particles.