Edd Sorenson, legendary cave diver, of Cave Adventurers...
Since I am also in the market for a light, I will share some more of what I understand. First off, the comparisons in Jackson are in very clear water, in the pitch dark. So those results are not necessarily applicable to your use in daytime NE wreck diving. At around 3:00 in the video you can compare the light beams easily, and you can see the 21 W HID has an almost laser-like quality, nearly parallel lines. I believe that is why they are described as having more "punch" in lower visibility water. The UWLD 15 is plenty bright, I'm guessing way more illumination overall but less compact beam. I have nothing against UWLD, it is currently my first choice (debating the 15 or 26) but I will use it mostly in cave diving.
From cavediver.net there is this comparison of the LM HID 21 and UWLD 26 which addresses the issue of beam focus:
Comparing the LM21 HID to the UWLD 26 LED
On Page 2 of that thread Bobby discusses how he has optimized his lights for clear water but I think it is also the nature of LED lighting. One of the participants sums it up pretty well, there is not going to be one ideal light for every condition.
Two other thoughts. It looks to me like LM is perhaps phasing out the LED 21 in favor of their newer LED 26 (don't quote me on this), which are actually priced comparably. Still above your price range, but might be worth considering. I think it is possibly a response to UWLD and evolving technology.
Lastly, the LM 21 HID can be bought with a smaller battery for under $1200, just sacrificing burn time, so closer to your price range.
