DawnT, the Canon G series cameras are pretty much the same as the S series except in size factor. They share much the same elements including sensor. The G series, at least in my estimation, is not a camera one would stick in a trouser pocket as you can with the S series. That WAS the deciding factor. If I had to carry a camera in the hand then I would continue to carry my DSLR. The Canon S95 is bigger than the Canon SD8xx series and to me verges on being almost too big.
Here is a comparison in size photo between the Canon SD850, Canon S95 and the iPhone 3G.