The flow and heat transfer inside HP compressor rotating disc cavities are buoyancy driven and are known to be extremely difficult to predict. The coupled nature of the disc thermal behaviour and the adjacent fluid flow within the disc cavity and shroud could form several interesting flow structures that are governed by the thermal boundary conditions.This makes the numerical modelling of such flows very challenging. Despite the use of URANS by several researchers to predict disc cavity flow-field, many LES studies reported in the literature argue that the overall structure and the small-scale features present in such flows cannot be captured by URANS due to turbulence modelling limitations. It has also been argued that URANS predicts advection of locally generated eddy viscosity to regions where it is unphysical and that it is unable to capture the buoyancy influences, stratification, rotation, and flow transition occurring within heated rotating cavities. All the while, URANS has been successfully used to capture the formation of single or multiple radial arms and the associated vortex pairs, and the formation of near-shroud flow structures such as the existence of circumferential vortex streaks. This paper presents comparisons between simulation results using URANS and LES and compare them with experimental data obtained from the Sussex multiple cavity rig. Both flow structure and thermal data are compared to further understand the differences between the two simulation methodologies from a thermal designer’s perspective.