In a large competition of fine shooters couldn't the results depend on how they were feeling that day? I like barrel alignments equally but seem to shoot better on game with o/u. I think it's easier to "get on to" the o/u than the double.

Having said that, how I'm feeling about a particular gun on a particular day---a little nostalgic for American classic, overseas fine gun or ducks on the plate---is the determinant of choice. And the notion guns are to be used.