towing line vs towing rope

towing line and towing rope both are nouns.

Word	Noun	Adjective	Verb	Adverb
towing line	Yes	No	No	No
towing rope	Yes	No	No	No

As nouns, towing line and towing rope are synonyms defined as:

Other synonyms of towing line include towline, towrope.

towing line (noun)	towing rope (noun)
(nautical) a rope used in towing	(nautical) a rope used in towing