Both Canon R6 II and Leica SL2-S have Full frame 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 Leica SL2-S'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 R6 II and SL2-S sensor size comparison.
Sensor Size and Resolution Comparison image of Canon R6 II and Leica SL2-S Cameras
Canon R6 II and Leica SL2-S have the same sensor sizes so they will provide same level of control over the depth of field when used with 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 R6 II
or the
Leica SL2-S ,
including hyperfocal distance.
