Just as I often go to the Rural Life Museum to test photo gear, I also shoot this scene routinely. For the above shot, I put the G12 in Av mode at f4.5, ISO 80, small Flexizone focus rectangle and widest zoom setting (28mme). The matching shutter speed was 1/1000 second. The matching G9 shot is below (except that somehow the f-stop was set to f4 on the G9). These are the untouched JPEGs straight from the cameras except for downsizing.
There isn't a lot of overall difference between the G12 and the G9 images except that the G12 image includes slightly more of the overall scene because of the wide angle lens (28mme vs 35mme). What about zooming in?
The picture above is from the G12 at maximum zoom and f4.5, 1/400 second. The 140mme telephoto of the G12 produces a bit wider view than does the 210mme of the G9 (f4.8, 1/250) shown below. The G9 choose to slightly increase exposure as compared to the G12. The G9 exposure is probably a result of the tighter zoom.
Not so apparent here, but it seemed to me that the G12 produced a slightly better image than the G9 when the focal lengths were forced to be the same; however, this may well be self-justification on my part. I do think that the shadow areas in G12 images showed slightly better detail.
I suspect that RAW images (which I also obtained) from the G9 and G12 might well be processed to have even fewer differences than these in-camera JPEGs. I'll give those RAW images a try after Adobe releases the necessary update to Camera Raw.