Notes:
The QE14 fare's Saturday night stay restriction is likely defined as requiring that the first flight of the last fare component in the priceable unit be on or after the first Sunday following the departure of the first flight of the first fare component in the PU. In the single circle-trip PU case, the relevant times will be the departure from SFO and the departure from DFW. In the two open-jaw PUs case, the relevant times will be the departure from DEN and the departure from BOS. Therefore from the perspective of the Saturday night stay restriction, the circle-trip choice is advantageous (more time passes between the two measurements).