Sigma Quattro H has a
45.0MP APS-H (26.6 x 17.9 mm ) sized CMOS (Foveon X3) sensor and features Dual TRUE III processor. On the other hand, Panasonic S1R has a
47.0MP Full frame (36 x 24 mm ) sized CMOS sensor and features Venus Engine processor.
Another similarity between these two cameras is that both Panasonic S1R and Sigma Quattro H sensors lack anti-alias (Low-Pass) filters. Removing anti-alias filter increases the sharpness and level of detail but at the same time, it increases the chance of moiré occurring in certain scenes.
Below you can see the Quattro H and S1R sensor size comparison.
As seen above, Panasonic S1R has a 1.8x Larger sensor area than Sigma Quattro H. 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.