The objective of this paper is to compare the results from large eddy simulations of laboratory-scale particle-laden forced plumes with the equilibrium-Eulerian and Lagrangian approaches. The comparison focuses on the transitional region and the low Stokes number regime, up to the boundary of the range of applicability of the equilibrium-Eulerian approach. Our analysis examines one-way and two-way coupling, gradually incorporating momentum and heat exchange effects between the gas and the solid phase. These simulations enable an investigation of how high particle mass fractions and the choice of modelling approach regarding particle dispersion affect quantities of interest in large eddy simulations of natural plumes. Comparison between the two particle-modelling formulations in one-way coupled simulations reveals satisfactory agreement for Stokes numbers based on the Kolmogorov time scale up to 0.2. However, for larger particle sizes, the equilibrium–Eulerian approach tends to overestimate preferential concentration, thus leading to an underestimation of gravitational settling and limiting its applicability to higher-inertia particles. This limitation can be more prominent in cases where an a priori estimation of the Stokes number is challenging due to the wide range of scales involved. In the two-way coupling regime, the mass fraction considered is 30% and the presence of a monodisperse population of low-inertia particles results in reduced specific momentum flux and entrainment rate along the axis of the plume. Although the agreement between the two models is satisfactory for mean values, there is a non-negligible impact on the transition to turbulence and second-order statistics. Finally, the incorporation of heat exchange between the gas and the particles shows a strong effect in the buoyant characteristics of the plume.