or so vs more or less

or so and more or less both are adverbs.

Word	Noun	Adjective	Verb	Adverb
or so	No	No	No	Yes
more or less	No	No	No	Yes

As adverbs, or so and more or less are synonyms defined as:

or so and more or less: (of quantities) imprecise but fairly close to correct

Other synonyms of or so include about, approximately, around, close to, just about, roughly, some.

or so (adverb)	more or less (adverb)
(of quantities) imprecise but fairly close to correct	(of quantities) imprecise but fairly close to correct
	to a small degree or extent