Sony A37 has a
16.0MP APS-C (23.5 x 15.6 mm ) sized CMOS sensor . On the other hand, Sony A6100 has a
24.0MP APS-C (23.5 x 15.6 mm ) sized CMOS sensor and features Bionz X processor.
Sony A6100's sensor provides 8MP more than Sony A37'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 A37 and A6100 sensor size comparison.
Sony A37 and Sony A6100 have the same sensor sizes so they will provide same level of control over the depth of field when used with same focal length and aperture. On the other hand, since Sony A37 has 49% larger pixel area compared to Sony A6100, it has potential to collect more light on pixel level hence have less noise in low light / High ISO images.