If you're going to be walking around in the dark with a gun you need to have a light mounted on it. You follow the safety rules don't you? How do you know what your gun is pointed at when you point your offhand light at something else? What if you drop the offhand light? IMIO (in my indisputable opinion) both lights are required and that little 60+ lumen handheld should be considered as as much a part of your gun as the magazine. My E2D "belongs" to my gun as much as the magazines and the Insight on the rail and they all live happily together in the safe, drawer, range bag or on my person. Call me crazy but I think being able to light up everything you point your gun at and anything else without pointing your gun at it is the obvious choice. And don't forget the laser.