Sony WX220 has a
18.0MP 1/2.3' (6.17 x 4.55 mm ) sized BSI-CMOS sensor and features Bionz X processor. On the other hand, Sony W320 has a
14.0MP 1/2.3-inch (6.17 x 4.55 mm ) sized CCD sensor .
Below you can see the WX220 and W320 sensor size comparison.
Sony WX220 and Sony W320 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 (2.01µm2 vs 1.56µm2) compared to Sony WX220, it has larger pixel area to collect light hence potential to have less noise in low light / High ISO images.