RE: Over Under or Side by Side?
For the most part, double triggers gives you the instantaneous choice of chokes. Lets say you are running a dog and a pheasant/quail/grouse flushes wild at 35 yds, you can immediately choose to shoot your tighter choke without going through a previous, "looser" pattern as you would have to if the barrels are set to fire in a particular order. Besides this and maybe the nostalgic factor, I can't see much more reason unless someone else offers some info.