OK, so each outfit changes a few stats, based on what Im seeing.
Schoolgirl does nothing.
Kimono increases Intelligence, Refinement, Sensitivity, Cooking and Cleaning.
Cowgirl increases Strength and all Combat Stats.
Catgirl increases Sensitivity.
Summer increases Intelligence but lowers the Defenses.
Winter increases Stamina, as well as the Defenses.
Party increases Refinement, Decorum, Art, Cooking, Cleaning, and Temperament.
Black increases Charisma, Sin, and Art, but lowers Morality.
Priestess increases Intelligence, Morality, Faith, and all Magic Stats, but lowers Sin.
Princess increases Intelligence, Refinement, Sensitivity, and Decorum.
Champion increases Stamina, Strength, and Intelligence, as well as the Skill Stats and Attack Stats.
Awesome Coat increases Stamina, Strength, and Charisma, as well as the Skill Stats and Attack Stats.
and
Jumpsuit increases Stamina, Intelligence, Faith, and both Defenses.
That's it.
Keep this alive so everyone can see this.