Both Nikon AW130 and Pentax RZ18 have 16.0 MP resolution sensors but Nikon AW130's sensor is 1/2.3' (6.17 x 4.55 mm ) and Pentax RZ18's sensor is 1/2.3-inch (6.08 x 4.56 mm ).
Since Nikon AW130's has a larger sensor area with the same resolution, this means that it also has a larger pixel area hence better light collecting capacity for a given aperture compared to Pentax RZ18.
Below you can see the AW130 and RZ18 sensor size comparison.
Nikon AW130 and Pentax RZ18 have almost the same sensor size, so neither of them has any significant advantage over the other in terms of providing control over depth of field when used with the same focal length and aperture.