Canon SX400 IS has a
16.0MP 1/2.3 (6.17 x 4.55 mm ) sized CCD sensor and features Digic 4+ processor. On the other hand, Olympus E-PL1 has a
12.0MP Four Thirds (17.3 x 13 mm ) sized CMOS sensor and features Truepic V processor.
Below you can see the SX400 IS and E-PL1 sensor size comparison.
As seen above, Olympus E-PL1 has a 8.0x Larger sensor area than Canon SX400 IS. 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.