The reflector size and design is important to throw (lux, not lumens). The larger, deeper, and smooth reflectors give the most throw (how far the beam will shine). The lumens (overall light going everywhere, not directed to any particular spot) has little to do with throw. The size of the LED is important to throw (smaller LED size, the better). For Cree brand LEDs, the smaller XR-E type throws farther than the XP-E and larger XP-G,and XM-L types. But the XR-E puts out less lumens than the larger XP-G and XM-L type LEDs.
LEDs use a driver to govern the amps delivered from the battery to the LED. The driver board that can provide the most amps without burning up the LED can give you more lumens and more lux (and use up the battery charge quicker).
LEDs driven hard will produce heat. It is good to have this heat transferred into the body of the flashlight, so the LED itself won't overheat and burn up (and reduce its output). So flashlight designs for "heat sinking" allow the LED itself to not overheat (but the flashlight body will feel warmer to you).
