This study employs mathematical models to compare and assess the relative performance of various composite membranes incorporated in a high-temperature membrane reactor. Two categories (porous and dense) and five types of composite membrane systems (Pd/Ag, polyimide, silica, inert porous and Ru-dispersed porous) have been considered. Also included in the study is the special case of the Pd/Ag composite system having imperfections (pinholes and cracks). Ethylbenzene dehydrogenation over promoted iron oxide catalyst has been studied as the model reaction. Overall, the dense systems show higher performance levels at lower membrane thicknesses. However, the porous composite systems, especially those in which active metal particles have been incorporated within the micropores, can be very useful due to their significantly higher contact surface to volume ratio. The study has also confirmed that high hydrogen permselectivity is a key factor in determining reactor performance in terms of conversion enhancement.