Both Canon T6s and Pentax K-70 have 24.0 MP resolution sensors but Canon T6s's sensor is APS-C (22.3 x 14.9 mm ) and Pentax K-70's sensor is APS-C (23.5 x 15.6 mm ).
Since Pentax K-70'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 T6s.
One other difference between these two cameras that is worth mentioning is that Pentax K-70's sensor doesn't have an 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 T6s and K-70 sensor size comparison.
Sensor Size and Resolution Comparison image of Canon T6s and Pentax K-70 Cameras
As seen above, Pentax K-70 has a 1.1x Larger sensor area than Canon T6s. 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.