For me, it's hard to beat the default unique duds most companions come in, but I've got to do something with all of the other unique apparel I find. And some of the less unique apparel just looks too cool to let it go to waste. Cait will always get the Grognak Costume, Hancock and Preston look equally snazzy in the Minutemen General's Uniform + Lieutenant's Hat from Ironsides. My pirate queen gave her first mate MacCready the Submariner's Uniform.
Settlers get different duds depending on their role. Shopkeepers I'll give pre-war business outfits, not necessarily clean ones. Farmers generally keep their default apparel, and guards and provisioners I'll equip appropriately for combat.