Just take a look at the data sheets and compare them...The G0 is the budget one and not as well spec'd as the G2. It has:
- slightly larger image sensor (1/2.9" vs 1/3") (however due to the additional 2MP, the G0 is comparably smaller)
- poorer low light performance (0.01 vs 0.003 lux minimum)
- smaller aperture (f2.0 vs f1.4)
- etc, etc
The G0 is cheaper for a reason. It's nowhere near as good and is shown as 'end of life' - avoid.