Oh, yeah, eyesight makes a big difference!
One of the things that happens as we get older is the pupils of our eyes don't open up as much in dim light. As a result, the advantage of larger exit pupils in binoculars is reduced, especially in dim light, because smaller eye-pupils can't take advantage of the "extra" light.
That's is pretty well-known, but another aspect of smaller eye-pupils is they tend to sharpen the view slightly, especially around the edges of the field of view--exactly like a smaller lens aperture in a camera sharpens the edges, and for the same reason: It reduces the amount of "edge" light, the rays that come in through the edges of the lens, which are deflected the most, both due to their distance from the center of the lens, and the interference of the lens mount.
However, this doesn't help the overall sharpness of older eyes. Instead it just reduces the difference in the perception of sharpness through optics.
Eyes also vary considerably in how they perceive color. One result is a lens system that emphasizes one color over another may look sharper to one person, and not to another.
There are other differences as well, the reason I try to gather several people now and then to look through a bunch of binoculars. It's always good to get a broader spectrum of opinions.
"Gunwriters, as you know, aren't as informed as their readers are and if it wasn't for the readers, there would be no need for writers..."--Shrapnel, May 2015