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The Z2 is the "CombatLight" with adjustable CombatGrip and Lanyard. Only in black. P60 Lamp.
The C2 is the version with Clip and Grip (non-adjustable). No lanyard. In either black or HA. P60 Lamp.
The M2 is the version with Clip, Grip (non-adjustable) and Shock Isolated Bezel. No Lanyard. Only in HA. With both P60 and High Output P61 Lamps.
The outer "surround" beam of the M2 is slightly smaller and slightly brighter because the Lamp Assembly is deeper within the Shock Isolated Bezel then in the standard bezel. I don't notice a difference in use but can tell the beams apart most of the time.
Pricing is down to may things. We could argue about it but at the end of the day, people have to justify the cost for themselves based on their requirements I guess. In general, I doubt most people need the M2.
Of the three, I would pick the M2 even though I don't need it.
From the range of standard sized SureFires (two SF123A), I would pick the G2Z model. (I don't find clips on such large flashlights useful since they are too big for EDC (every day carry) for the function they serve me). The only bulb model I would still consider for EDC is the A2.
The G2Z is light-weight, feature rich, extremely tough, and personally, I think it is one of the best models SureFires offers.
The L5 will be available to the public "soon". I hope before the end of the year.
Al