We perform a comprehensive comparison of FinFETs, stacked nanowires (stacked NWs), circular and square gate-all-around (GAA) n-FETs with same footprint, by using an in-house deterministic BTE solver accounting for quantum confinement, a wide set of scattering mechanisms and self-heating. We show that an increase in surface roughness (SR) can frustrate the improvement in on current, Ion, that for high-quality interfaces we observe in stacked NWs compared to FinFETs. Simulations suggest that SR also influences whether or not In0.53Ga0.47As can provide better Ion than strained silicon (sSi). © 2017 IEEE.