Both Canon T7i and Pentax K-3 II have APS-C sized 24.0 MP resolution sensors so sensor size and resolution is not a differentiator between these two cameras.
One other difference between these two cameras that is worth mentioning is that Pentax K-3 II'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 T7i and K-3 II sensor size comparison.
Sensor Size and Resolution Comparison image of Canon T7i and Pentax K-3 II Cameras
As seen above, Pentax K-3 II has a 1.1x Larger sensor area than Canon T7i. 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.
Sensor size sets the circle of confusion, so it drives how much depth of field each
of these bodies gives you at a given aperture. You can calculate it exactly for the
Canon T7i
or the
Pentax K-3 II ,
including hyperfocal distance.
