Samsung CL5 has a
9.0MP 1/2.5-inch (5.744 x 4.308 mm ) sized CCD sensor . On the other hand, Samsung PL170 has a
16.0MP 1/2.3-inch (6.08 x 4.56 mm ) sized CCD sensor .
Samsung PL170's sensor provides 7MP more than Samsung CL5'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 CL5 and PL170 sensor size comparison.
As seen above, Samsung PL170 has a 1.1x Larger sensor area than Samsung CL5. Larger sensors give photographer more control on the depth of field and blurry background compared to smaller sensor when shot in same focal length and aperture.