Sony A300 has a
10.0MP APS-C (23.6 x 15.8 mm ) sized CCD sensor . On the other hand, Samsung NX300M has a
20.0MP APS-C (23.5 x 15.7 mm ) sized CMOS sensor and features DRIMe IV processor.
Samsung NX300M's sensor provides 10MP more than Sony A300's sensor, which gives a significant advantage in real life. You can print your images larger or crop more freely.
On the other hand, please keep in mind that Max sensor resolution is not the only determinant of resolving power. Factors such as the optical elements, low pass filter, pixel size and sensor technology also affects the final resolution of the captured image.
Below you can see the A300 and NX300M sensor size comparison.
Sensor Size and Resolution Comparison image of Sony A300 and Samsung NX300M Cameras
Sony A300 and Samsung NX300M 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
Sony A300
or the
Samsung NX300M ,
including hyperfocal distance.