Was a C2 on the list??? JK...but, i would HIGHLY recommend the extra cost (or near same if purchased here on the marketplace). Knowing that you will be "using" your light, and not just playing with it, the clip on the C2 will greatly enhance the carry options, and allow you to "quickly" secure your light on some molle webbing with out having to try to get it in a pouch, etc., or allow you to secure it in your cargo pockets. Plus, your C2-HA will probably gome back looking alot nicer than the black Z2 or nitrolon G2 (they're both great lights, btw, but I honestly think the C2 will serve your purpose better). The C2 also has the rubber "combat grip", and is easier to hold than the Z2, as it has 4 square sides, as opposed to the Z2's 2 square sides, or the G2Z's roud body. They tend to wear into your fingers after awhile.
I just back from Iraq, and the clip on the C2 was real nice to keep the light from getting in an awkward position (BDU's/ACU's/ABU's have bigger pockets than civilians are used to), and it was real nice to be able to just "clip it" to my body armour. Also, +1 on the Malkoff (although the surefire P60L will do in a pinch). I also recommend an FM35 Red flip-up filter, when light and noise discipline is required.
Hope I was able to help...be safe and God Speed...oh, and :welcome:
EDIT: Sorry, just read your "EDIT"...get the Z2, sell it on the market place, and get a C2-HA! But I would go with the Z2 if that wasn't an option.