Panasonic S5 has a 24.0MP Full frame (35.6 x 23.8 mm ) sized CMOS sensor and features Venus Engine processor. On the other hand, Olympus E-M1X has a 20.0MP Four Thirds (17.4 x 13 mm ) sized CMOS sensor and features Dual TruePic VIII processor.
Another difference between these two cameras is that Panasonic S5's sensor lacks anti-alias (Low-Pass) filter. Removing anti-alias filter increases the sharpness and level of detail but at the same time, it increases the chance of moire occurring in certain scenes.
Below you can see the S5 and E-M1X sensor size comparison.
Sensor Size and Resolution Comparison image of Panasonic S5 and Olympus E-M1X Cameras
As seen above, Panasonic S5 has a 3.7x Larger sensor area than Olympus E-M1X. 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.