The G2 figures are the 'second generation' of the E Frontier/Content Paradise figure range, comprising of James, Koji, Kelvin and Simon (for the boys), and Jessi, Miki, and Sydney (for the girls), with, I understand, another female figure on her way at some point to act as Kelvin's opposite. The central idea behind them is that each gender shares a body mesh, whilst the heads are different. This means that clothes can be shared between characters more easily (so why there are clothes being specifically sold as being 'for Miki 2' is beyond me). The mesh and joint parameters are different from the original figures, and so clothes and texture which fitted the original characters will not work on new ones - much the same as V3's textures won't work on V4.

There are no real 'advantages' to using them over the original figures, or over any other figures, really - it's all a matter of personla preference, and whatever figure helps you get the job done. Of course, as with the older generation DAZ figures, new products soon stop being sold for the 'obsolete' figure range, and so there is a certain need to keep with the curve if you want to maintain your Poser addictin.

Hope that covers most of what you were asking,

JonTheCelt

EDIT Good grief. I just looked at my little thing to the left, and realised this is my 555th post! I didn't think I'd been that chatty!