Canon SX1 IS has a
10.0MP 1/2.3-inch (6.17 x 4.55 mm ) sized CMOS sensor . On the other hand, Nikon P520 has a
18.0MP 1/2.3-inch (6.16 x 4.62 mm ) sized BSI-CMOS sensor .
Nikon P520's sensor provides 8MP more than Canon SX1 IS's sensor, which gives a significant advantage in real life. You can print your images larger or crop more freely.
On the other hand, please keep in mind that Max sensor resolution is not the only determinant of resolving power. Factors such as the optical elements, low pass filter, pixel size and sensor technology also affects the final resolution of the captured image.
Below you can see the SX1 IS and P520 sensor size comparison.
Sensor Size and Resolution Comparison image of Canon SX1 IS and Nikon P520 Cameras
Canon SX1 IS and Nikon P520 have almost the same sensor size, so neither of them has any significant advantage over the other in terms of providing control over depth of field when used with the same focal length and aperture.
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 SX1 IS
or the
Nikon P520 ,
including hyperfocal distance.