Sony NEX-C3 has a
16.0MP APS-C (23.4 x 15.6 mm ) sized CMOS sensor and features Bionz processor. On the other hand, Canon SL3 has a
24.0MP APS-C (22.3 x 14.9 mm ) sized CMOS sensor and features DIGIC 8 processor.
Canon SL3's sensor provides 8MP more than Sony NEX-C3'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 NEX-C3 and SL3 sensor size comparison.
Sony NEX-C3 and Canon SL3 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.