Both Sony TX30 and Sony WX220 have 18.0 MP resolution sensors but Sony TX30's sensor is 1/2.3-inch (6.16 x 4.62 mm ) and Sony WX220's sensor is 1/2.3' (6.17 x 4.55 mm ).
Since Sony TX30'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 Sony WX220.
Below you can see the TX30 and WX220 sensor size comparison.
Sony TX30 and Sony WX220 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.