spiff up vs smarten up

spiff up and smarten up both are verbs.

Word	Noun	Adjective	Verb	Adverb
spiff up	No	No	Yes	No
smarten up	No	No	Yes	No

As verbs, spiff up and smarten up are synonyms defined as:

Other synonyms of spiff up include slick up, spruce, spruce up, titivate, tittivate.

spiff up (verb)	smarten up (verb)
make neat, smart, or trim	dress and groom with particular care, as for a special occasion
	make neat, smart, or trim