So I finally got the chance to play with the M2 xml2 and it is definitely a winner!
At first I was kind of disappointed when I first turned it on. First, I'm a big fan of neutral tint lights around 4500k and this was a bit cooler. It's nothing annoying though, and considering the intended purpose of this head, max output and efficiency is more important. The tint of the led used is great for this purpose, so I can't fault it for that. Second, I thought that the spill would be tighter than what it was. As it is, the spill is actually just a hair tighter than my Nailbender OP XML P60. When I used it outside, however, I found that the width of the spill really didn't affect the performance of this head. The hotspot is incredibly tight and incredibly bright. And because of this, your depth of field isn't affected very much because of the brightness of the target in the distance.
The hotspot I would estimate the width to be about 1/2 smaller than the Nailbender. It's not quite as tight as a 4Sevens G5 with xpg, although it's hard to say because the G5 has a pretty sharp transition from hotspot to spill whereas the M2 xml2 has a very nice gradual fade. If anything I would say the G5 is about 40% tighter than the M2 xml2. This gradual fade, though, makes it very nice to look at as it doesn't keep your focus solely on the hotspot.
The throw on this thing is about the best I've seen for such a compact light using an xml2. I would say the throw is equivalent to the G5 but, of course, with a much wider coverage. This is actually pretty amazing if you consider that the depth of both reflectors are about the same, but significantly wider on the G5 and uses a much smaller led.
In this test, I was using a bored C2 with a two year old AW 2900mah 18650 (not fully charged) and a mcclicky switch. Not the optimal setup. I'm sure if I used something like a Panasonic NCR18650 and a zerores switch, I would get significantly higher output.
I have to say, I had some reservations about the M2-50/M2-xml/M2-xml2. Mainly because it was a direct drive setup. One output. No regulation. And for my main purposes for using flashlights (camping, hiking, backpacking) it wasn't an ideal setup, but considering you can use this with a single cr123 or rcr123, it's versatility is not all that limited. I'm so glad I picked one up. I love love LOVE the fact that someone was able to utilize the larger size of the M2 head to increase the throw of a larger led setup. There just aren't that many options if you want a 6P form factor with good throw and high output, but this head does it and does it extremely well. In a tactical or SAR scenario, this light is ideal. Small size. Great output and throw. Single mode. Bulletproof.
And it definitely has the looks!