Nikon L28 has a
20.0MP 1/2.3-inch (6.16 x 4.62 mm ) sized CCD sensor . On the other hand, Canon SX150 IS has a
14.0MP 1/2.3-inch (6.17 x 4.55 mm ) sized CCD sensor and features Digic 4 processor.
Nikon L28's sensor provides 6MP more than Canon SX150 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 L28 and SX150 IS sensor size comparison.
Nikon L28 and Canon SX150 IS 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.