Sony TX66 has a 18.0MP 1/2.3" (6.17 x 4.55 mm ) sized BSI-CMOS sensor and features BIONZ processor. On the other hand, Olympus E-PL7 has a 16.0MP Four Thirds (17.3 x 13 mm ) sized CMOS sensor and features TruePic VII processor.
Below you can see the TX66 and E-PL7 sensor size comparison.
As seen above, Olympus E-PL7 has a 8.0x Larger sensor area than Sony TX66. 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.