Both Fujifilm X-T1 IR and Canon 1D MIV have 16.0 MP resolution sensors but Fujifilm X-T1 IR's sensor is APS-C (23.6 x 15.6 mm ) and Canon 1D MIV's sensor is APS-H (27.9 x 18.6 mm ).
Since Canon 1D MIV'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-T1 IR.
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 1D MIV sensor size comparison.
As seen above, Canon 1D MIV has a 1.4x Larger sensor area than Fujifilm X-T1 IR. Larger sensors give photographer more control on the depth of field and blurry background compared to smaller sensor when shot in same focal length and aperture.