Barrel length should have no bearing on patterns, that is controled by the choke. Longer barrels provide a longer sighting plane and sometimes can smooth out the swing on crossing shots. Use what your comfortable with, my shotguns have several barrel lengths and I use them for different applications. Grouse and Woodcock I have a 24" barrel on my M59 auto, my waterfowl and pheasant guns have 26" or 28" barrels. I tend to shoot the 28" a little better not sure why. Good luck.