What's the real difference b/w G2, G3, G8?

I know G8 is the updated version of G3, which is updated of G2... and I know that as you move up the chain the figures have more posable/customizatble parts... for the novice user, what's the *real* difference though? Do G8 figures pose more realistically in common poses (i.e. does one figure "sit" better than another)? Does Michael 7 render in more detail than Michael 6? Or is it more like this year's model or a t-shirt vs last years - a few new colors, but really it's the same thing.
For background, I am trying to figure out under what circomstances I might wish to use one figure vs another. G2 clothing is a lot cheaper and i have a lot of it, and it fits G2 better than it fits G3... but why might I want to use Michael 7 vs Michael 6?
Comments
Each new figure include changes supposed to make them more realistic than the previous one, for example bend better, have better expressions, and so on.
One of the main changes between G2 and G3 for example is that G3 introduced facial bones, which enable finer control of expressions, while G2 had to use morphs for expressions.
However just because G3 was released does not mean G2 is obsolete, if you have G2 content and character you like there's nothing stopping you from using them.
<<One of the main changes between G2 and G3 for example is that G3 introduced facial bones, which enable finer control of expressions, while G2 had to use morphs for expressions>>
OOOHHH yes, that's exactly what i was looking for.
<However just because G3 was released does not mean G2 is obsolete, if you have G2 content and character you like there's nothing stopping you from using them.>
Of course, but understanding the difference helps. So, for example, if I know i need a close up of a face with an espression, i might need a higher gen figure, but if i am rendering someone's back it doesn't make a difference. But before you said that, I wouldn't have known :)
Genesis 8 has far better and more realistic facial expression capabilities and better posing than Genesis 3. But you can easily use the skins of G3 on G8 if you a particular skin or make up. There is a thread around on how to convert Genesis 3 Female morphs to Genesis 8 as well if you have favorite characters in that line. I wasn't keen on moving up another generation but was sold by the better expressions. So I am working on moving all of my characters up to Genesis 8 to take advantage of that particular feature.
If you use a skin converter to convert 3Delight skins to Iray, like the Anagennesis product or the skin converters from VGDigitime, even V4 can look gooodin a close up.