If your iris dilates up to 7mm, a 7mm exit pupil will have the image as 'washed out' as when seen by the unaided eye. If you're one of the rarer creatures for whom the iris expands to larger than 7mm, a 7mm exit pupil will have the sky a little darker, or less 'washed out' than as seen by the unaided eye.
Contrary to somewhat common thinking, an urban sky is still dark enough to cause one's iris to dilate to maximal. Only when notably bright light sources, or awfully brightly lit scenery, falls within one's field of vision might your irises contract somewhat.
For given magnification, it does not hurt to have an exit pupil as large as or larger than one's iris. Even though the sky is made brighter by a larger exit pupil, so too are the objects seen through the sky glow. While intrinsic contrast is not altered, the brighter scene results in a relatively smaller contribution by visual system noise, which does improve the detection of slightly subtler contrast.
The darker sky rendered by a smaller exit pupil (at given magnification) is principally an aesthetic benefit, but with a small cost in reduced contrast discrimination and general reduction in depth of penetration (when limiting to more typical binocular-sized exit pupils.)