Sitting further away from the 32-inch to achieve the same sharpness would make the 32-inch display appear the same size physically as the 27-inch.
Also, they would need to enlarge the content as the distance between them and the display increases so that text remains legible.
There would be no benefit in getting the larger display and sitting further away in this case.
If you run 32" and 27" UHD displays at the same pixel resolution and same viewing distance then the 32" will show everything larger.
If you run 32" and 27" UHD displays at the same pixel resolution and correct the distance got get the same apparent size then the 32" has the advantage of not needing your eyes to focus as close as for the 27" and the disadvantage of needing a deeper desk.
Depending on your eyes that can be an important difference.
If you run 32" and 27" UHD displays at different pixel resolutions to achieve the same apparent scaled pixel density, at the same viewing distance everything will have the same size, the 32" gives more screen real estate, and the 27" will be a bit sharper.
Assuming 110ppi as the preferred layout pixel density, as is the case for all Apple 27" and 32" displays, then neither a 32" nor a 27" UHD displays can be used without indirect rendering with scaling, i.e. nothing will be pixel perfect.
The edge cases with pixel perfect rendering, a 27" UHD in 1920x1080 retina and a 32" UHD in 3840x2160, might be interesting for people with very bad and very good eyesight, respectively. In that case the 32" gives 4x the screen real estate of the 27".
Personally I use 27" 2560x1440 displays at native resolution.
