Sony W320 has a
14.0MP 1/2.3-inch (6.17 x 4.55 mm ) sized CCD sensor . On the other hand, Sony WX350 has a
18.0MP 1/2.3-inch (6.17 x 4.55 mm ) sized BSI-CMOS sensor .
Below you can see the W320 and WX350 sensor size comparison.
Sony W320 and Sony WX350 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. On the other hand, since Sony W320 has 28% larger pixel area compared to Sony WX350, it has potential to collect more light on pixel level hence have less noise in low light / High ISO images.