I'm confused by the differences in the literature. In short, does the Canon G3X have a larger sensor than the G16?
Yes, the G3X sensor is larger. From Canon's product pages,
- The G3X has a 20.2 Megapixel, 1.0-inch CMOS sensor.
- The G16 has a 12.1 Megapixel, 1/1.7-inch CMOS sensor.
Confusingly, a 1-inch sensor does not directly translate to any dimensional inch. Its nomenclature is a historical holdover from television camera tubes. Roughly, a 1" sensor has an approximately 16mm diagonal. For sensor sizes relative to 1", such as the G16's 1/1.7" sensor, scale accordingly.
Thus, the G3X's sensor is about 16mm diagonal. It has a crop factor relative to 35mm full-frame of 2.72. The G16's sensor is about 9.4mm diagonal. It's 35mm-relative crop factor is 4.55.
Put another way, the G3X's sensor is 1.7 times larger (linearly) than the G16 sensor. It has 1.7² = 2.9 times the area of the G16 sensor.