NRG' s insulation placement is more energy efficient than an ICF's. Why? When thermal mass is exposed to a building's interior, it moderates the indoor air temperature. NRG's thermal mass does just that. Compare that to an ICF. An ICF places a layer of insulation between the thermal mass and the building interior, which greatly diminishes the effect of the thermal mass.
Because the thermal mass effect in an ICF is minimized due its insulation configuration, an ICF requires more insulation to have the same thermal performance as an NRG block. See below for a more in depth explanation. Follow the science. Then act.