Both Sony TX5 and Sony TX7 have 1/2.4-inch sized 10.0 MP resolution sensors so sensor size and resolution is not a differentiator between these two cameras.
Below you can see the TX5 and TX7 sensor size comparison.
Sony TX5 and Sony TX7 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 Sony TX7 has 11% larger pixel area (3.12µm2 vs 2.80µm2) compared to Sony TX5, it has larger pixel area to collect light hence potential to have less noise in low light / High ISO images.