I don't want to challenge the physics, but I wonder about physiology. For example, if our head is mechanically clamped, we have some difficulty precisely localizing a sound source. We move our head constantly and this helps the localization process. This is why binaural listening is not always as stunning as one might expect. A great example of this is if the recording is done with microphones attached to a live head and the recording individual walks around the room. The listeners perception is muddled because the sound changes as if there is movement, but this movement does not correspond to the listener's own movement.

In this respect, I wonder how eye movement influences our sense of detail. For example, at specific viewing distance some of the 8K pixels might fall between our rods and cones. However, with eye movement these intermediate pixels will be discovered. I haven't seen any research about this, but I think that it is likely that our response will be similar to the auditory interpretation while our head is moving. At minimum I think that we will qualitatively perceive that more detail is available and assign a (+) to that image, compared to a lower resolution image.

But, humans are very sensitive to the color gamut. It's a difficult choice to assign "best" if the 4K image has a wider color gamut than the 8K image.