Sony W330 has a
14.0MP 1/2.3-inch (6.17 x 4.55 mm ) sized CCD sensor . On the other hand, Nikon S570 has a
12.0MP 1/2.3-inch (6.17 x 4.55 mm ) sized CCD sensor and features Expeed processor.
Below you can see the W330 and S570 sensor size comparison.
Sony W330 and Nikon S570 have the same sensor sizes so they will provide same level of control over the depth of field when used with same focal length and aperture.