Sony A77 II has a 24.0MP APS-C (23.5 x 15.6 mm ) sized CMOS sensor and features Bionz X processor. On the other hand, Samsung NX500 has a 28.0MP APS-C (23.5 x 15.7 mm ) sized BSI-CMOS sensor and features DRIMe 5 processor.
Another difference between these two cameras is that Samsung NX500'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 A77 II and NX500 sensor size comparison.
Sony A77 II and Samsung NX500 have almost the same sensor size so none of them has any significant advantage over other in providing control over depth of field when used with same focal length and aperture.