observing vs observant

observing and observant both are adjectives.

Word	Noun	Adjective	Verb	Adverb
observing	No	Yes	No	No
observant	No	Yes	No	No

As adjectives, observing and observant are synonyms defined as:

observing and observant: quick to notice; showing quick and keen perception

observing (adjective)	observant (adjective)
quick to notice; showing quick and keen perception	paying close attention especially to details
	(of individuals) adhering strictly to laws and rules and customs
	quick to notice; showing quick and keen perception