pony cart vs donkey cart

pony cart and donkey cart both are nouns.

Word	Noun	Adjective	Verb	Adverb
pony cart	Yes	No	No	No
donkey cart	Yes	No	No	No

As nouns, pony cart and donkey cart are synonyms defined as:

Other synonyms of pony cart include ponycart, tub-cart.

pony cart (noun)	donkey cart (noun)
a cart with an underslung axle and two seats	a cart with an underslung axle and two seats