or so vs just about

or so and just about both are adverbs.

Word	Noun	Adjective	Verb	Adverb
or so	No	No	No	Yes
just about	No	No	No	Yes

As adverbs, or so and just about are synonyms defined as:

or so and just about: (of quantities) imprecise but fairly close to correct

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

or so (adverb)	just about (adverb)
(of quantities) imprecise but fairly close to correct	(of quantities) imprecise but fairly close to correct