The g10 VZ grips from kabar are what I'll refer to, as they make sense here, and are quite different to other g10.
The VZ's are smooth except for the textured patch in the middle. The smooth parts are nearly indistinguishable from other high density polymers, not too dissimilar to the stock nylon. The textured part is just that- the same material, carved into a very, very aggressive grip, only to be used on knives whose handles don't move in hand during normal use.
If you're talking textured g10, like a spyderco (and I assume the tkc's, though maybe they're smooth?), then the feel isn't too dissimilar to, say, nylon that you'd taken some coarse sandpaper to. Hard to describe, I suppose.
But yeah, it's essentially just strong, hard, dense plastic, and all depends on the texture of the specific grip you're looking at.