Here are some pictures of my "new" G6. As could be better seen in the comparison to the G3, G9 and G12, the G6 is relatively large.
Although some must like it, I don't care for the mode dial being on the back of the G6. I very much prefer that it be on top as it is in the G3, G9 and G12.
The articulated display screen was not included in the G9 and I missed it very much. The articulated display on the G12 is significantly larger, brighter and higher resolution.
The hand grip on the G6 was larger than the one on the G3. The G9 had no grip at all which led to Richard Franiec creating and marketing an add-on grip. Canon must have been listening because the grip returned -- albeit in a much smaller size.
The G3 and G6 have informational displays on top whereas the G9 and G12 do not; however, I have to admit that I quickly became accustomed to the control dials on top and informational display on the back LCD of the G9 and G12.