Both Fujifilm X-T20 and Canon T6i have 24.0 MP resolution sensors but Fujifilm X-T20's sensor is APS-C (23.6 x 15.6 mm ) and Canon T6i's sensor is APS-C (22.3 x 14.9 mm ).
Since Fujifilm X-T20'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 Canon T6i.
Another difference between these two cameras is that Fujifilm X-T20'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-T20 and T6i sensor size comparison.
Sensor Size and Resolution Comparison image of Fujifilm X-T20 and Canon T6i Cameras
As seen above, Fujifilm X-T20 has a 1.1x Larger sensor area than Canon T6i. 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.