I would go for the 12ZM with so called "CombatGrip" because it makes holding and aiming it so much easier.
I love this flashlight, but I would go for a SureFire M6 because I love it even more. I think the M6 is more powerful than the 12PM/ZM. It's ability to output a whiter, brighter 500Lu beam without 'thermal shutdown' is a big advantage.
As for the 12PM/ZM and the M6 being the brightest flashlights... That depends on what you mean and want.
If you want the brightest light for size, then SureFire's are the ones. If you want a spotlight with a 6"+ reflector for distance illumination, then how about the RC3800. Far cheaper, but I've never used one so I don't know really how it compares.
"The Lectro Science NiteTracker RC3800 2 Million CP Rechargeable Spotlight will run 15-20 minutes on a charge. [~$65]"
If you are looking for a small flashlight with light output that seems impossible, then the 12ZM is for you. If you want more runtime, go for the M6.
Both these flashlights (RC3800 & 12PM/ZM) have short burntimes, so you should have loads of DL123As (very light; easy to carry) or a 12V/mains charging source...
