Fujifilm X-Pro3 has a
26.0MP APS-C (23.5 x 15.6 mm ) sized BSI-CMOS sensor and features X-Processor 4 processor. On the other hand, Nikon D7100 has a
24.0MP APS-C (23.5 x 15.6 mm ) sized CMOS sensor .
Another similarity between these two cameras is that both Nikon D7100 and Fujifilm X-Pro3 sensors lack anti-alias (Low-Pass) filters. 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 X-Pro3 and D7100 sensor size comparison.
Fujifilm X-Pro3 and Nikon D7100 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 Nikon D7100 has 8% larger pixel area (15.28µm2 vs 14.12µm2) compared to Fujifilm X-Pro3, it has larger pixel area to collect light hence potential to have less noise in low light / High ISO images.