Both Olympus TG-3 and Olympus SH-3 have 16.0 MP resolution sensors but Olympus TG-3's sensor is (1/2. ) and Olympus SH-3's sensor is 1/2.3' (6.17 x 4.55 mm ).
Since Olympus SH-3'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 Olympus TG-3.
Below you can see the TG-3 and SH-3 sensor size comparison.
As seen above, Olympus SH-3 has a infx Larger sensor area than Olympus TG-3. Larger sensors give photographer more control on the depth of field and blurry background compared to smaller sensor when shot in same focal length and aperture.