product line vs line of products

product line and line of products both are nouns.

Word	Noun	Adjective	Verb	Adverb
product line	Yes	No	No	No
line of products	Yes	No	No	No

As nouns, product line and line of products are synonyms defined as:

product line and line of products: a particular kind of product or merchandise

Other synonyms of product line include business line, line, line of business, line of merchandise.

product line (noun)	line of products (noun)
a particular kind of product or merchandise	a particular kind of product or merchandise