Glad to see the reference to narrow vs wide sighting plane. I wish the quote of single vs double sighting plane would die or better yet didn't exist.
I love shotguns wether SxS, O/U, semi or pump. If they are well built and fit me. When it come to SxS vs O/U you have to compare apples to apples. Field gun to field gun. Target to target. If you take a well balanced , long barrelled target O/U against an equal SxS ( pigeon or fouling piece) you will be surprised how similar they are.
I believe and I think it has been proven over time that you can be more precise with the narrower sighting plane of an O/U than with the wider of the SxS. Most all competition is shot with an O/U, even driven shooting in the UK has shifted to them.
Now in a grouse or woodcock cover. Give me a light weight (6-6 1/2 lbs) 28 inch, straight grip,SxS that fits and I will be a very happy man.