XML2-U2 does NOT product 1000 lumen at all. If you look at the data sheet on page 3, U2 driven at 2A is only outputting about 728 lumen. I have DGX600 myself. While I don't have the instrument to measure lumen, I do have proper equipment to measure current accurately at work. DGX600 with flash charge battery is consuming about 1.1A only. Given the lost in the driver, my guess is the actual current into the U2 is like 900mA, which makes about 400 Lumen by my estimation.
I also have DRIS 1000 (3C) and DRIS 1K shorty (3AA). From brightness point of view, it is really hard to tell them apart. I would say 3C ~=> DGX > 1K (3AA), but difference is slight. My estimation based on current measurement is 3C is 400-450. 1K is 300. From beam angle point of view, DGX is very similar to 1000 (3C). 1K (3AA) is slightly wider. In all practical purpose, they are the same
I would choose base on your usage, not brightness or beam angle. 3C has much better run time than the other two. So if I need a backup for cave diving, 3C is my choice. If you want to put the light on soft good man, DGX's size is the best of them. It will go for about 2 hour in full brighness with 2500mAh cell, it is perfect for a 2 tank rec charter. Overall, I like them all.
I have no experience with the 450 focusable
DGX goes for about 2 hour with 2500mAh cell.