Leica V-Lux 20 has a
12.0MP 1/2.3-inch (6.08 x 4.56 mm ) sized CCD sensor . On the other hand, Leica V-Lux 30 has a
14.0MP 1/2.3-inch (6.08 x 4.56 mm ) sized CMOS sensor and features Venus Engine FHD processor.
Below you can see the V-Lux 20 and V-Lux 30 sensor size comparison.
Leica V-Lux 20 and Leica V-Lux 30 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 Leica V-Lux 20 has 16% larger pixel area compared to Leica V-Lux 30, it has potential to collect more light on pixel level hence have less noise in low light / High ISO images.