Panasonic ZS3 has a 10.0MP 1/2.3-inch (6.08 x 4.56 mm ) sized CCD sensor . On the other hand, Samsung ST600 has a 14.0MP 1/2.3-inch (6.08 x 4.56 mm ) sized CCD sensor .
Below you can see the ZS3 and ST600 sensor size comparison.
Panasonic ZS3 and Samsung ST600 have sensor sizes so they will provide same level of control over the depth of field when used with same focal length and aperture. On the other hand, since Panasonic ZS3 has 40% larger pixel area compared to Samsung ST600, it has potential to collect more light on pixel level hence have less noise in low light / High ISO images.