The DR light claims a 10 degree spot.
The D620 specs on LeisurePro say it's a 14 degree spot.
DR claims 3500 lumens on their website, but I just watched a video of Jared Hires talking about the HP50 and he said 2500. Since Cree says the XHP50 max is 2500 lumens, I'm inclined to believe 2500 vs 3500.
The D620 claims 2700 lumens. But, it uses a Cree XHP70, which Cree says has a max of 4K lumens.
It would be really interesting to get the two lights side by side and see which one is actually brighter. The DR claiming an output equal to the LED's max suggests to me that the actual out-the-front lumens would be less. OTOH, the D620 claiming 2700 from an LED that can put out 4000 suggests that maybe their rating is actual out-the-front lumens. In which case, the D620 may be noticeably brighter.
Orrrr, the D620 is only putting out 2700 raw, in order to have decent burn time with only 4 x 18650. In which case, I would expect both lights to be pretty close in brightness.
If the latter is the case, having a bigger can on the D620 that lets it put out the full 4000 lumens that the LED is capable of and still have 1.5 - 2 hours of burn time would make it a spectacular light.