Shorter barrels are lighter and easier to move around with in the woods. Your pattern has more to do with your choke than barrel length. A longer barrel does a few things. It helps the natural aim of the shotgun and lets it swing better I think. It can also increase muzzle volecity, to a point. A shorter barrel on a turkey gun is really not a bad thing then. You are not shooting on the fly and most modern powders reach maximum volecity quick enough that a longer barrel will not make a difference.

So basically it is just more convenient for the hunter.

Paul