Both Canon G15 and Nikon P330 have 1/1.7-inch sized 12.0 MP resolution sensors so sensor size and resolution is not a differentiator between these two cameras.
Below you can see the G15 and P330 sensor size comparison.
Sensor Size and Resolution Comparison image of Canon G15 and Nikon P330 Cameras
Canon G15 and Nikon P330 have the same sensor sizes so they will provide same level of control over the depth of field when used with same focal length and aperture.
DxOMark Sensor Scores
DxOMark is a benchmark that scientifically assesses image quality of camera sensors. It scores camera sensors for color depth (DXO Portrait), dynamic range (DXO Landscape) and low-light sensitivity (DXO Sports), and also gives them an overall score. Canon G15 and Nikon P330 sensors have been tested by DxO and the results show that P330 has a better overall score of 54, 8 points higher compared to G15's score of 46.
Model
Overall
Color Depth
Dynamic Range
Low-light ISO
Canon G15
46
19.9 bits
11.5 Evs
165 ISO
Nikon P330
54
21.0 bits
11.7 Evs
213 ISO
Sensor size sets the circle of confusion, so it drives how much depth of field each
of these bodies gives you at a given aperture. You can calculate it exactly for the
Canon G15
or the
Nikon P330 ,
including hyperfocal distance.