I agree with part of surefire's argument. The polymer in the G2 is cheaper to buy, and far cheaper for manufacturing, than aluminum. And I do think it should be a bump below the 6P in price. However, I think eventually it will be -- once the G-2 isn't so new, and the distribution channels are completely geared up, supply&demand will get more reasonable and the G-2 will fall in price.
I also think that the G2 does have some real advantages over the aluminum versions. One, it's lighter and so more carryable....... That might not be important for everyone but is to me. Two, if it is true that the polymer protects the lamp assembly better, that's a huge advantage. I still consider the fragility of the lamp to be a real and alarming weakness for SureFire.
Regarding Brock's buy order, I'd go this way. If I want bang-for-the-buck for a tactical (that implies use with a handgun) use, the 6Z is it. Yes, the M2 is a step up, but I think we're talking about serious diminishing returns here, for an extra, what, $40 is price? For pure carryability and useability for utility use, the E2 will be awesome, definitely the top choice. Other than the E2, for utility the G2 has the nod if you want minimum price and weight, 6P is probably best bang-for-the-buck, and the D2 has some interesting added features but suffers from dimishing returns like the M2.
Were I to be stuck with 3 choices, it'd probably be:
E2: carry everywhere utility light
6Z: dedicated tactical light, stays with firearm in quick-open safe.
E1: for when I want to totally minimize on space.
If I absolutely needed a waterproof light, I'd substitute M2 for 6Z.