The nearest I can tell, I will give up 4 to 6 birds, on a round of 100, by shooting the S x S, compared to my MX-8s.
We can debate whether or not there really is a disadvantage to shooting the S x S in sporting clays all day long, and never reach a consensus. That was not my purpose in starting this thread. I already KNOW that the disadvantage is real. I only put this forth as a reasonable explanation as to why. I will continue to hunt with my S x Ss, and compete with them in S x S venues, but never again will I attempt to compete in a major sporting event with one. I enter them to try to win, and one bird can be huge in a 200 bird event. I shot in a team tournament yesterday afternoon. Four man teams, 100 bird course. Our team won the event, and $1000, by ONE BIRD! We shot a 360, next team had a 359.
The only shotgun game I can think of where there may be an advantage to shooting a really good handling S x S is box birds. What pigeon shooting I have done has been with a O/U, but the next time it will be with a S x S. Pigeons is a game of elevation, mostly. A S x S may well give a better perspective of elevation distance. One of the greatest pigeon shooters of the modern era, Billy Perdue, thought so, and only used S x Ss.
SRH