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. On the other hand, Leica V-Lux 20 has a
12.0MP 1/2.3-inch (6.08 x 4.56 mm ) sized CCD sensor .
Below you can see the V-Lux 30 and V-Lux 20 sensor size comparison.
Leica V-Lux 30 and Leica V-Lux 20 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 (2.31µm2 vs 1.98µm2) compared to Leica V-Lux 30, it has larger pixel area to collect light hence potential to have less noise in low light / High ISO images.