I cannot prove this, obviously, but I believe that most people who claim to favor "instant choke selection" don't shoot a shotgun enough to be able to choose, in a split second, which barrel/trigger to go to. That would take determined, rigid training to get ingrained into your shooting. I have shot two trigger guns since I was eight years old (I'm now 64), but not exclusively. I see two triggers as no disadvantage to high scores in sporting clays, but I do see the S x S, overall, as a disadvantage, as much as I enjoy them.
I would really like to look over the list of competitors and the scores at that shoot you mention, salopian. Could you provide a link to it? Certainly a "large clayshooting competition" would have the scores posted somewhere on the 'net.
SRH
Stan, I could not agree more. As primarily a hunter who gets in maybe 5-10 visits to the range annually, and someone who hunts with DT SxS, I am almost never selecting the trigger. I don't have time, most of the time. However, I am using barrels with different chokes and I want them different. Because I am thinking of the odds of the likely shot. IMHO, when one is hunting for a specific quarry (Pheasant, Sharpies, Ruffs, jump shooting ducks or ducks over decoys) it's not hard to know what the likely shot/required choke will be, first and second.