Nikon S570 has a
12.0MP 1/2.3-inch (6.17 x 4.55 mm ) sized CCD sensor and features Expeed processor. On the other hand, Nikon S220 has a
10.0MP 1/2.3-inch (6.08 x 4.56 mm ) sized CCD sensor .
Below you can see the S570 and S220 sensor size comparison.
Nikon S570 and Nikon S220 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.