Canon 5D MII has a 21.0MP Full frame (36 x 24 mm ) sized CMOS sensor and features Digic 4 processor. On the other hand, Sony A77 II has a 24.0MP APS-C (23.5 x 15.6 mm ) sized CMOS sensor and features Bionz X processor.
Below you can see the 5D MII and A77 II sensor size comparison.
As seen above, Canon 5D MII has a 2.4x Larger sensor area than Sony A77 II. 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.
DxOMark Sensor Scores
DxOMark is a benchmark that scientifically assesses image quality of camera sensors. It scores camera sensors for color depth (DXO Portrait), dynamic range (DXO Landscape) and low-light sensitivity (DXO Sports), and also gives them an overall score. Canon 5D MII and Sony A77 II sensors have been tested by DxO and the results show that A77 II has a better overall score of 82, 3 points higher compared to 5D MII's score of 79.