i got both mine from costco. so £600 for S10 and £800 for G15.
i would have definately stuck with S10 if it hadn't have buuzzed so loud.
is G15 worth £200 more.......well to me picture quality on both have been superb and i can't see any difference. G15 is bigger screen and higher spec so have to assume technically its better?
it has other bells and whistles S10 doesn't have but they are both the same as far as tweaking picture goes.
so short answer 'no'.