Going to a “favorite decade” themed party. (Not a costume party) Which outfit should I wear?

I have a party to go to Friday night that is “wear your favorite decade”. I happen to have 2 authentic 60’s/70’s dresses that could work: the Hawaiian kaftan or the polyester geometric dress. Which one should I wear? I do have to say that I did wear the geometric dress to a party with the alot of the same people so they’ve already seen this dress. The kaftan hasn’t ever been worn.

EDIT: If I wear the kaftan I can wear my natural hair. If I wear the geometric dress then I have to either straighten my hair and do a Farrah Fawcett feathered hair or wear a wig which I don’t really want to do.