Beauty is mostly subjective, but art is not, which is why there are prosfessional art critics.
Side by side development coincided with the Art Nouveau period, roughly from the end of the war btween Prussia and France (1870s) to the beginning of WWI. The influence of Art Nouveau on double gun design is obvious.
Then came Art Deco. Streamlined shapes and emphasis on form as opposed to surface embellishment, ie engraving, was the mark of that period.
American pump shotguns from the Winchester Model 12 and later display obvious Art Deco influences, as does an Airstream trailer and other items designed in that period. Which is to say that the lines developed by the London makers do not have a monopoly on artistic appeal.
Some of us appreciate Arte Deco objects more than Art Nouveau ones, and therefore consider the lines of the lowly Stevens 620 just as seductive as those of the finest London best side by side.
I never owned a pump, but that does not alter the fact that there is visual appeal in its lines, especially in the smaller gauges. From that point of view I would say that American shotguns rank ahead. But they are not doubles, so I guess they cannot be considered in this forum.
