OP has already said that there is no cost saving: "I am looking at one PNR only. But I have two options at the same price"
so as mentioned by several posters above, I fail to see any difference in conditions if he books as A to B and B to C instead of A to C via B if both same flights under one PNR. I'm not sure what he means by a "coupon" anyway unless there's somewhere in the world still issuing wax backed tickets.

As an aside, making a single PNR booking for identical connecting flights/timings as multi sector rather than a journey with connection can oddly sometimes make a saving - I recently booked a J ticket on QR via DOH where it was 30% cheaper on identical flights from a certain European city to Oz via DOH booked as a multi-sector, perhaps due different fare categories offered for individual sectors or just a serendipitous anomaly....