Olympus SZ-31MR iHS has a
16.0MP 1/2.3-inch (6.17 x 4.55 mm ) sized BSI-CMOS sensor and features Dual TruePic V processor. On the other hand, Olympus XZ-10 has a
12.0MP 1/2.3-inch (6.17 x 4.55 mm ) sized BSI-CMOS sensor .
Below you can see the SZ-31MR iHS and XZ-10 sensor size comparison.
Olympus SZ-31MR iHS and Olympus XZ-10 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 Olympus XZ-10 has 35% larger pixel area (2.38µm2 vs 1.76µm2) compared to Olympus SZ-31MR iHS, it has larger pixel area to collect light hence potential to have less noise in low light / High ISO images.