preferred vs preferable

preferred and preferable both are adjectives.

Word	Noun	Adjective	Verb	Adverb
preferred	No	Yes	No	No
preferable	No	Yes	No	No

As adjectives, preferred and preferable are synonyms defined as:

preferred (adjective)	preferable (adjective)
more desirable than another	more desirable than another
preferred above all others and treated with partiality