Beam difference between Gerber IU and IU-M

A couple weeks ago I bought a Gerber Infinity Ultra M from lighthound.
Yesterday a Gerber Infinity Ultra arrived from batterystation.
I noticed the head was quite different:

Then I fed it an Eneloop and was rather surprised by the different beamshape.
Holding the two together about 4" away from a piece of paper, the contrast is obvious. Ultra M is on the left.

I'm guessing the difference is because a tighter beam is more useful to the military in terms of light discipline, but should the Ultra-M be noticeably dimmer?

Supposedly (I'm not in spec-ops, so I can only ASSume), the tighter beam minimizes the changes of someone spotting the light in situations such as in closed quarters and you're in a room you're not supposed to be in looking at papers.

The lower output is likely due to the LED in the Ultra-M being recessed and surrounded by metal resulting in less light coming out of the LED package. In contrast, the standard IU has most of the LED out of the housing allowing the light to come out from most every portion of the LED housing. I love my IUs. I've tested them to provide enough light for dark indoors navigation for 5-6 days straight (never turned it off).

I have the IU and prefer its spot/spill pattern. For me, it's the perfect utility light, especially in tight, dark quarters. It always travels in my pocket and is my most-used light. My PT Attitude is close behind though. They both have reasonable output and long runtimes.
:rock:

I found the ultra-m beam useless for my purposes and I gave it away within days of receiving it.

W.