Higher efficiency? Not likely. My 2-cell MagLED module in a 2D MagLite (essentially an early MagLED) draws around 860mA when cold while my 2-D Rebel MagLED draws 1660mA. That's almost twice the amp draw to get a 50-60 lumen advantage over the older, less efficient, version. Now, if you take a Seoul SSC P4 U-bin and swap that onto an older MagLED module then it will be approximately as bright as the Rebel light but with a larger hotspot due to the shallower reflector. Swap in an even more efficient emitter like an XP-G R4 or R5 and it will be brighter and last longer. That's one huge advantage that the older MagLED module has over the newer version of the light: the LED can be upgraded fairly easily. Add the lower amp draw, making the batteries last longer, and you have a winner, in my book. The one advantage that the Rebel MagLED has is that deep reflector giving you an even tighter hotspot for more throw.