Barrel length has very little to do with performance anymore. The newer powders will burn fast enough to be complete in just about any legal length barrel. And patterns have more to do with the choke than the barrel length.
The only thing a longer barrel will do is help the barrel swing better if you have a problem with follow thru. The down side is it doesn't react as fast. A longer barrel will also give you a longer sight plane, which could possibly make you more accurate.
However a lot of god shotgun shooters don't even look at the bead. A good fitting shotgun should naturally point where you look. You should concentrate on your target, not the end of your barrel. This is very hard for rifle shooters to do though, take my word for it.
Paul