Don't want to get into a peeing match here but I think everyone will agree that all shotguns evolved as the most efficient tools to harvest fast moving, usually airborne game. If you don't agree just try it with a handgun or rifle, you'll get the point. Doubles were the only practical way to make a multi shot gun dating back to the 1700's and beyond, although there were a few experimental guns made with more barrels. By the time the earliest successful multi shot pump and autoloading repeaters appeared on the scene the side by side had been largely perfected in it's many forms as the graceful, efficient and reliable tool that it still is today. It's pretty hard to improve on perfection. The fly in the ointment was the fact that this type of gun required mostly very skilled hand labour to produce, leaving the door open to a gun which could be mass produced quickly and inexpensively for the exploding new market as settlers spread across North America.
Enter the inexpensive mass produced pump and autoloading guns. These guns were concieved, produced and sold mostly in the United States in vast numbers. They were designed to a different concept than the typical British or European game gun. The North American game such as ducks, geese, pigeons, swans, shore birds, prairie chickens and the occasional rabbit, possum or squirrel seemed inexhaustilble at this time and it was free for the taking for anyone that had a suitable gun. The pumps, autoloaders were designed to be inexpensive to buy, rugged enough for heavy waterfowl loads and durable. With no bag limits and vast flocks of birds high magazine capacity was an advantage. For the type of hunting at the time handling characteristics and aesthetics took a back seat, a duck hunter didn't need or appreciate a gun that fitted and pointed like his finger. If it was affordable, rugged and reliable he didn't care if it was heavy as a truck axle, handled like a 2x4 , rattled when you shook it and looked like a contraption, it went bang when he pulled the trigger. At the same time, a flood of cheap nasty $ 3-5 Belgian hardware store doubles arrived for those who couldn't afford a new pump or auto and had no appreciation for the fine doubles.
Today the situation is totally different. No more shooting as many birds as you can, fill the wagon. Guns for waterfowl are limited to three shots, no lead allowed. Reduced bird numbers, bag limits and restricted access are a fact in many areas and hunting has become recreational rather than survival. The pump and auto are still excellent tools for waterfowl where mobility and versatility are not as important but the light well made and well balanced double still excels on upland game because of it's better handling characteristics and instant choice of chokes for two different distances. A shotgun is not aimed like a rifle for use on moving targets, it is pointed instinctively like pointing your finger. Aim it and you'll miss. You keep your eyes on the target not the sights like a rifle or pistol. The front bead is for reference for alignment, it is not a sight and a centre bead only really has application on premounted trap type target shooting. On a properly fitted gun ( yes, could be a pump or double) when the stock is properly cheeked and mounted to the shoulder your master eye will look straight down the centre of the rib at the right height to put your shot where you're looking. With a gun that really fits you practice your mount anywhere, practice shooting on the range until instinct is paramount and results in repeatable success. Then you will understand what all this fuss about fine double is about. Jim