Sony W550 has a
14.0MP 1/2.3-inch (6.17 x 4.55 mm ) sized CCD sensor and features BIONZ processor. On the other hand, Panasonic SZ3 has a
16.0MP 1/2.3-inch (6.08 x 4.56 mm ) sized CCD sensor .
Below you can see the W550 and SZ3 sensor size comparison.
Sensor Size and Resolution Comparison image of Sony W550 and Panasonic SZ3 Cameras
Sony W550 and Panasonic SZ3 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.
Sensor size sets the circle of confusion, so it drives how much depth of field each
of these bodies gives you at a given aperture. You can calculate it exactly for the
Sony W550
or the
Panasonic SZ3 ,
including hyperfocal distance.