The snow let up for a while so I did some outdoors testing of the PD40 against the foursevens S12/MMU. Both these lights are awesome! The tint on the SST-90 in the MMU is good but the PD40 is a beautiful creamy neutral white by comparison. The PD40 is pure flood and lights up the whole world with an even beam without a sharp hot spot contrast. The MMU is pretty floody but with a wide focused hot spot. Beyond 70 to 100 yards I would choose the MMU if I had to see detail. The PD40 is a great high power flood light while the S12/MMU combines good flood with moderate throw. The PD40 has more levels than the MMU and the momentary burst mode that can be easy accessed from any level is a big plus. The build quality on both is excellent!
After the first few minutes it looked like I was losing the burst mode on the PD40 again. This was no doubt because of the lower capacity four year old cell I was using that couldn't keep up with the demands of the 1600 lumen burst mode. It is hard to decide which light to grab when heading out the door as they are similar size, weight, and shape and both put out an incredible number of lumens. The output of the PD40 is more pleasing with its smooth warm flood but the hot spot of the S12/MMU allows more reach while still producing a good flood. As you can see I am rambling in indecisiveness here
I hope these casual observations are useful.