Nikon D3200 has a 24.0MP APS-C (23.2 x 15.4 mm ) sized CMOS sensor and features Expeed 3 processor. On the other hand, Canon T6 has a 18.0MP APS-C (22.3 x 14.9 mm ) sized CMOS sensor and features Digic 4+ processor. Nikon D3200's sensor provides 6MP more than Canon T6'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 D3200 and T6 sensor size comparison.
Nikon D3200 and Canon T6 have almost the same sensor size so none of them has any significant advantage over other in this area.