Sony TX20 has a
16.0MP 1/2.3-inch (6.17 x 4.55 mm ) sized BSI-CMOS sensor and features BIONZ processor. On the other hand, Pentax P70 has a
12.0MP 1/2.3-inch (6.17 x 4.55 mm ) sized CCD sensor .
Below you can see the TX20 and P70 sensor size comparison.
Sony TX20 and Pentax P70 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 Pentax P70 has 32% larger pixel area (2.34µm2 vs 1.76µm2) compared to Sony TX20, it has larger pixel area to collect light hence potential to have less noise in low light / High ISO images.