Samsung ST700 has a
16.0MP 1/2.3-inch (6.16 x 4.62 mm ) sized CCD sensor . On the other hand, Canon SX30 IS has a
14.0MP 1/2.3-inch (6.17 x 4.55 mm ) sized CCD sensor and features Digic 4 processor.
Below you can see the ST700 and SX30 IS sensor size comparison.
Samsung ST700 and Canon SX30 IS 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.