Nikon P300 has a 12.0MP 1/2.3-inch (6.17 x 4.55 mm ) sized BSI-CMOS sensor and features Expeed C2 processor. On the other hand, Nikon L28 has a 20.0MP 1/2.3-inch (6.16 x 4.62 mm ) sized CCD sensor .
Nikon L28's sensor provides 8MP more than Nikon P300'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 P300 and L28 sensor size comparison.
Nikon P300 and Nikon L28 have almost the same sensor size so none of them has any significant advantage over other in providing control over depth of field when used with same focal length and aperture.