I got to wonder if other factors are involved with the popularity of O/U shotguns for shooting clays.
True, you dont see them at the ranges, but I dont think its because they're less accurate.
I'm no pro, but I can hit my share of clay pigeons with my SxS.
I think the main reason is because of the adjustable chokes many of those other guns offer. My SxS is choked for IC and Mod. That's it and that's all it ever will be. So it is limited to closer ranges for breaking clay,but for hunting I feel the difference is minimal
Many shotgun fanatics that shoot trap only will only use a single barrel shotgun because of where the pattern hits and over and under and/or side by sides
barrels are more difficult to regulate so as to match where the patterns are going to hit. It is one of the reasons (but not the only one) why clay shooters spend so much on their shotguns. The less expensive over and under are almost never regulated correctly anymore. Even some of the newer Brownings are defective in barrel regulation from the factory.
For those of you reading here that don't shoot trap:
This might not be a huge difference but even a slight error in regulation can make all the difference in clay competitions. (Understand that if a trap shooter hits 80% of his/her targets they are barely considered competition ready. Many competitions may have the top shooter at 100% with 2nd place missing only one target out of 100.)
Again, to me at least, it is all about results. I want the gun to be more capable than I am, not the reverse Shooting clays or hunting makes no difference to me regarding results. I do understand the nostalgia of a side by side however, but that is a topic all to itself. (There must be some reason I hang on to guns I haven't fired in 50 years.)
As to changeable chokes, I think most serious shotgun shooters are (as you stated) in love with them but mostly because some makers make better chokes than others. Most skeet shooters shoot skeet and skeet chokes in both barrels and most serious trap shooters shoot full and full or extra full and extra full and don't change them. Five stand and sporting clay shooters do use different chokes in different barrels. Personally I shoot a fixed choke full and full for trap because it is a dedicated trap gun. Hunting birds is a different story but I also shoot 28 gauge on brush quail, moving up to a 20 gauge in a more open field or for close range pheasant. Finally I move to 12 gauge for longer range pheasant so that is far beyond just chokes.
All of this is, of course, just my opinion.