One other element to add to the mix- some of us have an eye condition that causes the front sight to "double" through an aperture, IF the aperture's too big.
The human eye perceives light that comes through a set of sights in different ways, depending on age, astigmatism, and the physical characteristics of the sights themselves.
I wouldn't make the broad statement that the case is "closed" in favor of apertures.
Over the years I've worked with literally hundreds of guns, with all sorts of sight set-ups.
My eye, through a typical aperture (say AR15, for example) now sees a double image of the front post.
I can still shoot decently through such a setup, but not as well at longer distances because the front post's outline is not clear.
This is not a matter of that sight being blurry, the shooting glasses take care of that, it's a matter of seeing a doubled outline, very similar to two posts partially super-imposed against each other.
Reduce the size of the aperture, letting less light through, and it clears up the outline of the post.
But- it also covers up much more of the target & immediate area around it.
I can use a larger aperture ghost ring & do have it on a Marlin Guide Gun, in conjunction with a large & very visible front sight, but that's for quick-reaction shots inside 50 yards, not for pinpoint accuracy out beyond 100.
What I've found over the past 10 years or so is that I can now do better when accuracy's a key goal with a GOOD set of notch & post sights.
By good, I mean one with a solid front blade or post that's big enough to see (no tiny beads) and a well-dimensioned rear notch that provides just enough light on both sides to easily center the front blade in it.
Wide & shallow notches combined with tiny indistinct beads are too much work, don't define the front sight sufficiently well, and are a nuisance to work with.
The right "fit" between notch & post also more clearly defines the front sight outline, for me, and eliminates the doubling I get with a typical aperture.
I'm not saying this'd be the case for everybody, and I'm certainly not saying "case closed" based on my own experiences, but I AM saying that there's no granite-chiseled one-size-fits-all solution to finding the right sight configuration.
The aperture works well for a large percentage of shooters, but its efficiency is dependent on the size of the aperture and the eye of the shooter, combined with the visibility of the front sight.
How a sight combo transmits light to the eye matters, and for many it's a matter of experimenting till you find one that works best for YOU, as an individual.
Last week when I put three .357 holes under an inch with the Henry levergun, it was because those sights, with that big bead, gave me a clear sight picture (not to mention an accurate barrel helping).
I seriously doubt I could pull that off with a standard-sized aperture anymore.
Just can't get a clear front sight through one.
On the Ruger International with the Merit, yes; I can dial that one way down till the light transmission through the aperture clears up the front blade.
Point being that you try till you find the best solution for YOU.
Denis