middle distance vs vista

middle distance and vista both are nouns.

Word	Noun	Adjective	Verb	Adverb
middle distance	Yes	No	No	No
vista	Yes	No	No	No

As nouns, vista is a hypernym of middle distance; that is, vista is a word with a broader meaning than middle distance:

middle distance: the part of a scene between the foreground and the background
vista: the visual percept of a region

Other hypernyms of middle distance include aspect, panorama, prospect, scene, view.

middle distance (noun)	vista (noun)
the part of a scene between the foreground and the background	the visual percept of a region