My experience with file sizes related to print sizes typically goes like this:
A: "You can't make a sharp NxN" print from an NxN pixel file."
B: "Yes I can, and I have."
B fetches one or more examples.
A looks closely at it or them with some degree or other of purse-lipped annoyance.
B smiles.
-Dave-
When you compare prints on a wall from a normal viewing distance, it is going to be practically impossible to see.
Pixel peeping on screen will reveal difference. (I don’t pixel peep, a want to see the final print, old school)
But there is more under the hood going on than sharpness rendering. Getting a picture ‘sharp’ is digitally only a matter of calculated pixel manipulation.
Try some foliage on distance, try some pattern where the sensor pattern and RAW converter gets upset, and then you start to see the difference between a relative low pixel sensor and a high. And you start seeing the difference with a small sensor and bigger sensor.
The difference I see in my files is definition in those difficult areas.
When I switched over from my 2.4mp 2Dh to a 6mp d70, it was a visual difference in print. And when I got my first Kodak, that was out of space. (Reason could be the psychedelic moiré effects)
In analog period, I made a print and hung it on the wall and looked at it at normal distance and under the light where the print would hang, but things changed, images seldom make it to a print and are judged on screen on pixel level. And then posted on the web on 1200px wide............
Well.