The two handheld lights primarily differ in their battery. The bodies of the lights are almost identical in size and also use the same single-die LED with the same 1100+ raw LED lumen rating. Although both lights use a protected lithium-ion rechargeable battery, the 600 uses an a widely available18650 3.7V 3000 mAh battery that requires an separate external AC charger and the 700 uses an uncommon and more expensive 21700 3.7V 5000 mAh battery that contains an internal USB charger. The 21700 battery used in the 700 also better supports high-drain applications; bottom line the 700 has more power. The 700 can drive the LED to produce a little more light than the 600 although we doubt most divers will notice a difference in-water, but more importantly the 21700 battery in the 700 is capable of delivering 50% to 100% more burn time than the 18650 battery. We describe the proven DGX 600 as having a maximum 60 minute burn time, but the newer DGX 700 delivers up to a 90 minute burn time with a gradually dimming but still usable light for another 90 minutes.