Nikon L31 has a 16.0MP 1/2.3' (6.17 x 4.55 mm ) sized CMOS sensor . On the other hand, Panasonic FP2 has a 14.0MP 1/2.3-inch (6.08 x 4.56 mm ) sized CCD sensor and features Venus Engine IV processor.
Below you can see the L31 and FP2 sensor size comparison.
Sensor Size and Resolution Comparison image of Nikon L31 and Panasonic FP2 Cameras
Nikon L31 and Panasonic FP2 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.