Your comment just shows you don't understand what he wrote. His critique is affected not at all by the existence of higher magnetic fields.
ITER's volumetric power density is 400x worse than a PWR. ARC's is just 40x worse. Lidsky was pointing out DT fusion reactors are always going to be (generously) 10x lower in volumetric power density than fission reactors, due to limits on handling the power flowing through the first wall. Higher magnetic fields let ARC be better than ITER, but still sucking relative to fission reactors.
ITER's volumetric power density is 400x worse than a PWR. ARC's is just 40x worse. Lidsky was pointing out DT fusion reactors are always going to be (generously) 10x lower in volumetric power density than fission reactors, due to limits on handling the power flowing through the first wall. Higher magnetic fields let ARC be better than ITER, but still sucking relative to fission reactors.