My bad. My assumption when comparing was to have as identical an image as possible as the basic starting point, including perspectives. As such, your case 1 is outside the scope of my scenarios. As for your case 2, if one were to use the FF equivalent for focal length and f-stop, then the DoF is exactly the same whether APSC and FF are used, which I believe is the point made by others. As for the overall point about DoF being the only point, then using a camera with a 1inch sensor or a camera phone will achieve even greater depth of field for your case 1 – both of which are cheaper and much lighterI'll make you simpler what ReflexVE is saying.
Let make two cases:
A- R6 mk II
B- R10
Both uses an RF 85 f1.2
Both use the same exposure triangle, let's say f1.2 1/1000s 100iso, for the very same scene, shot in the very same moment
Subject will be kept of the same size in the frame, so with the R10 he'll be some steps behind to account for the crop effect.
He will end up with two pictures of the same resolution (both camera have 24mpx), with the same subject.
Both pictures will have same brightness, because exposure triangle is the same.
Subject's eyes will be more likely both in focus in the R10 picture, because to have the same subject size, he stepped back, meaning the lens uses a longer focus distance, meaning the DoF is more then the DoF you'll get in the very same picture shot with R6II.
Dynamic range is different between FF and Aps? He doesn't care, because it's not the point.
Noise is different between FF and Aps? He doesn't care, because it's not the point.
What he does care is:
-He gets with R10 the same picture I get with R6II, with the same exposure, but he gets more DoF then me, that is the thing he cares about
-He gets what he wanted with a camera smaller and lighter then mine; and if available, he could have used an 85 f1.2 specific for Aps, so smaller and lighter.
OR
Or he could have achieved the same thing with a 50 f1.2 (FF or Aps lens it's not important) without stepping back, but still achieving more DoF then me because he's using a wider lens, a 50, compared to my 85, so he gets more DoF for the same exposure, and the same aperture of course, even when the focus distance is the same.
Many talks about "how much light get to the sensor, let's calculate it"; well, for the same exposure triangle, for the same EV of a given scene, the light falling on a sensor or a film is exactly the same, regardless you're using a medium format or a smartphone, regardless of the lens you're using.

I do not want to enter into a debate about whether APSC or FF is a better system, as both have their pros and cons, although both can achieve the same DoF with the right settings, or that diffraction sets in ‘early’ for APSC at lower f-stop (but that’s not the point as you said). I think the main difference between the two systems is that in terms of available camera bodies and lenses, the FF format provides more choices with higher quality in general. This is the case not because FF is better in principle (for that matter one can also say that a large format is better than FF because it has a larger sensor), it is simply that most manufacturers have focused on FF (Fuji is a notable exception, and they do have quality apsc lenses and bodies). Given what is available, FF seems to be a reasonably natural point to rally around, but apsc, with it lighter weight and pricing, can be rather appealing to photographers as well. As for unique apsc images, I am really curious as to what apsc can produce that FF can’t. (I know, I know, this is not the point as it is all about DoF, but if I recall correctly, an earlier post did say something to this effect). Perhaps someone who knows about this can share samples for our collective education?
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