Sony a3500 has a
20.0MP APS-C (23.5 x 15.6 mm ) sized CMOS sensor and features BIONZ processor. On the other hand, Fujifilm X-S10 has a
26.0MP APS-C (23.5 x 15.6 mm ) sized BSI-CMOS sensor and features X-Processor 4 processor.
Fujifilm X-S10's sensor provides 6MP more than Sony a3500'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.
One other difference between these two cameras that is worth mentioning is that Fujifilm X-S10'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 a3500 and X-S10 sensor size comparison.
Sensor Size and Resolution Comparison image of Sony a3500 and Fujifilm X-S10 Cameras
Sony a3500 and Fujifilm X-S10 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 a3500 has 31% larger pixel area compared to Fujifilm X-S10, it has potential to collect more light on pixel level hence have less noise in low light / High ISO images.
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 a3500
or the
Fujifilm X-S10 ,
including hyperfocal distance.