Well, I'm an optical designer and completing my PhD in optics, so I can help...
You approach this topic in a way that will not allow for an accurate answer. If you prfer, you do not ask quite the right question
There are two reasons why lenses wide open are not quite as good as stopped down.
The first relates to optical effects on the sides of a lens. Especially true with spherical lens elements, but applicable in any case, you will get more aberrations from the borders, because the curvature "seen" by light rays will be more important (I'm simplifying, but that's the basic explanation). CA, coma, etc, all these aberrations are more important from the sides.
The second effect is vigneting. What causes vigneting is that, at wider apertures, all the areas of the image frame get different illumination (this is not the same as thinking that you "see" part of the iris, as some think). This effect is mitigated when closing down the aperture because only the center of the lens is used to create the image. The rays are more parallel to the axis of the lens.
Of course, it really depends on how the lens is made, so you cannot just compare lenses by specs.
A prime lens (or a refractive telescope) is designed and optimised for one set of parameters. For a zoom, it's about compromise, you cannot optimise everything for every focal length (you usually pick a focal length somewhere in the middle of the range and start from there). A reflecting telescope (with mirrors) works basically in the same way, but the light rays never enter in any material, they are only reflected, which in theory yields better images (reflecting telescopes do have other flaws, such as bokeh and they have their lot of CA/coma issues too, again because of the border effets).
So there is no physical reason why telescopes should be better, but there are design reasons why they might be. The less compromises you have to make, the better your results.
I had to design a 240x beam expander (a refractive telescope, in fact) for my PhD. It had to be optimized for one single wavelength (or colour, if you prefer). It's really near perfect at that wavelength, but you cannot imagine how crappy it is at other wavelengths! But since there is no need for it to be any good except at the wavelength I wanted, no one cares...
Physics are cool