Echoing what has already been said, it is a matter of taste, and the tartan. Some tartans when pleated to stripe have the "lawn chair" or "convict"(horizontal stripes) effect. Personally I like the look of the pleated to stripe when the opening of the pleat reveals a contrasting colour!. My most recent kilt, MacLaine of Lochbuie red modern is pleated to sett, although it could have been pleated to stripe. Just personal choice.