Now I'm no expert on handguns, so I'm interested in whether my assumptions are correct or not.
The UltraS is a big, heavy flashlight with a near Bezel switch. If produces a longer range beam, and I would think that in a Low light/no light environment, using a handgun for longer range targets is not the most accurate. The 12ZM is shorter, more light-weight, and designed for maximium light output with a beam that can be used for internal close range illumination.
Where the 12ZM and UltraS differ is that the UltraS does not make a good close quarters illumination tool compared to the 12ZM, that does not have the runtime to offer the more "duty" style runtime of the UltraS.
A more narrow, more intense beam (such as what I've read the UltraS has [no photo comparisons yet I notice]) allows the UltraS to be more useful for illuminating at longer ranges, but the poor beam quality compared to SureFires means that potentially, using UltraS could give you tunnel vision and fail to illuminate the whole surroundings. Now I would think that often, the target will not be bore-sighted in the centre of your beam when you first turn on the light. Having a high quality surround beam allows you to more quickly locate target and these factions of seconds could prove vital in the encounter.
I am sure the UltraS is a worthy comparison to the MagCharger in terms of output for the same beam quality, but for a more high-risk situation in which targets must be identified with only short bursts of light, a higher quality beam is vital. The ability to use the light is often more important then the amount of light.
Al