Well, I have tested such things, Bob, and it makes a significant difference indeed. At one time I had a whole stack of glass samples from all over the world. I had the stupidity to let a rare piece of Zeiss coated glass slip from my hands the other day, which came from a custom lot and is hence probably irreplacable. Fortunately, I
had a fresh piece sitting in a large contact frame I never use and cut it down for the 8X10 carrier. It takes a
very special cutter. Antinewton gets fussy because the pattern of the texture is related to angle of incidence
as well as depth of field - in other words, what works well for one size film and one type of image grain might
not be ideal for another. Optical coating might help suppress rings, but in my foggy climate it certainly doesn't.
Secondary reflections, ease of cleaning, etc are factors however. Ideally, one would make a fluid mount carrier,
but even to me that sounds like too much hassle. Of course, ordinary window float glass is way better than
no glass at all, because it at least keeps the film flat.