Wow, dems a lot of questions.
1. I don't have one but from what I can garner it seems that they are FUNCTIONALLY equivalent to a 6P Classic but without the aluminum body, lockout tailcap, anti-roll bezel and Pyrex lens.
2. Compare to the 6P above. Difference between E2e includes all of the above -- plus the G2 does not have the handy pocket clip of the E2e.
E2e uses different lamp assembly -- you cannot use the P60/P61 lamp assemblies as the E2e uses a special lamp that runs for 75 mins at 60 lumens (NOT 60 mins at 65 lumens like the 6P Classic and G2 Nitrolon).
You also cannot convert the E2e to a rechargeable light ... you can do so with the G2 by purchasing the KR1 kit.
Lastly, I do not believe any of the Surefire filters or LED conversions will work with the G2.
3. Polymer is cheaper to use than hard anodized aluminum. As you may or may not know, the manufacture of aluminum involves a relative large expenditure of electricity ($$$), leading to the nickname "canned electricity".
4. If you don't need any of the above differences, by all means get the G2. At $30 per light, it's very hard to beat that deal.