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, Ricoh GXR A12 50mm F2.5 Macro has a 12.0MP APS-C (23.6 x 15.7 mm ) sized CMOS sensor and features GR engine III 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 moire occurring in certain scenes.
Below you can see the X-T1 IR and GXR A12 50mm F2.5 Macro sensor size comparison.
Fujifilm X-T1 IR and Ricoh GXR A12 50mm F2.5 Macro have almost the same sensor size so none of them has any significant advantage over other in providing control over depth of field when used with same focal length and aperture.