Really a very personal matter of feel as to what works best for each of us. I personally prefer 28" barrels on doubles whether SxS or O/U on a hunting gun. For clays even longer is fine. For a pump or semiatuo I use both 26" and 28" and have no real preference unless I'm in tight quarters. For crow hunting where I might be hiding in thick tangles I like a barrel as short as 22" to 23" even.