new town vs urban area

new town and urban area both are nouns.

Word	Noun	Adjective	Verb	Adverb
new town	Yes	No	No	No
urban area	Yes	No	No	No

As nouns, urban area is a hypernym of new town; that is, urban area is a word with a broader meaning than new town:

new town: a planned urban community created in a rural or undeveloped area and designed to be self-sufficient with its own housing and education and commerce and recreation
urban area: a geographical area constituting a city or town

Other hypernyms of new town include populated area.

new town (noun)	urban area (noun)
a planned urban community created in a rural or undeveloped area and designed to be self-sufficient with its own housing and education and commerce and recreation	a geographical area constituting a city or town