Both Canon SL3 and Pentax KF 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 KF'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 SL3 and KF sensor size comparison.
Sensor Size and Resolution Comparison image of Canon SL3 and Pentax KF Cameras
As seen above, Pentax KF has a 1.1x Larger sensor area than Canon SL3. 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 SL3
or the
Pentax KF ,
including hyperfocal distance.
