I can't compare the HID light with the Blackwater, since I've never seen the latter.
I have the HID light. It's a nice little package, with a tiny lighthead, and the battery has the advantage of being able to be mounted on a standard BC because of the clip attachment. However, the beam is not intense or tightly focused. I found it to be better than any hand-held light in Puget Sound, but not nearly as useful as the focused HID lights made by Manta (Green Force) or Salvo. (My favorite piece of gear, hands down, is my Salvo 21W HID, even if I had to mortgage my house to buy it.)
On the other hand, the design of the Nite Rider light is very durable, the bulb tolerates a lot of abuse, and the customer service is absolutely superb.
In the price range, you're looking at the Nite Rider or the Dive Rite 10W. I'd recommend the latter for thick, turbid water.