Samsung NX300 has a
20.0MP APS-C (23.5 x 15.7 mm ) sized CMOS sensor and features DRIMe IV processor. On the other hand, Pentax KF has a
24.0MP APS-C (23.5 x 15.6 mm ) sized CMOS sensor and features PRIME MII processor.
One other difference between these two cameras that is worth mentioning is that Pentax KF's sensor doesn't have an 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 moiré occurring in certain scenes.
Below you can see the NX300 and KF sensor size comparison.
Sensor Size and Resolution Comparison image of Samsung NX300 and Pentax KF Cameras
Samsung NX300 and Pentax KF have almost the same sensor size, so neither of them has any significant advantage over the other in terms of providing control over depth of field when used with the same focal length and aperture.
Sensor size sets the circle of confusion, so it drives how much depth of field each
of these bodies gives you at a given aperture. You can calculate it exactly for the
Samsung NX300
or the
Pentax KF ,
including hyperfocal distance.