Nikon L31 has a 16.0MP 1/2.3' (6.17 x 4.55 mm ) sized CMOS sensor . On the other hand, Samsung ST80 has a 14.0MP 1/2.3-inch (6.08 x 4.56 mm ) sized CCD sensor .
Below you can see the L31 and ST80 sensor size comparison.
Sensor Size and Resolution Comparison image of Nikon L31 and Samsung ST80 Cameras
Nikon L31 and Samsung ST80 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.