Fujifilm X-T1 IR has a
16.0MP APS-C (23.6 x 15.6 mm ) sized CMOS X-TRANS II sensor and features EXR Processor II processor. On the other hand, Sony A500 has a
12.0MP APS-C (23.5 x 15.6 mm ) sized CMOS sensor and features Bionz processor.
Another difference between these two cameras is that Fujifilm X-T1 IR'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-T1 IR and A500 sensor size comparison.
Fujifilm X-T1 IR and Sony A500 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.