Both Fujifilm X-A10 and Nikon D5100 have 16.0 MP resolution sensors but Fujifilm X-A10's sensor is APS-C (23.6 x 15.6 mm ) and Nikon D5100's sensor is APS-C (23.6 x 15.7 mm ).
Since Nikon D5100's has a larger sensor area with the same resolution, this means that it also has a larger pixel area hence better light collecting capacity for a given aperture compared to Fujifilm X-A10.
Another difference between these two cameras is that Fujifilm X-A10's sensor lacks 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 X-A10 and D5100 sensor size comparison.
Fujifilm X-A10 and Nikon D5100 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.