I hunt with 24" to 28". I shoot better with my 28" barrel, but enjoy hunting with the 24" more. I've got two guns with 26" barrels, neither is one I can hunt with too much. I'm getting ready to by another 26" gun that I'm hoping becomes my primary duck hunting gun.
It's all feel and fit. I think the shot reaches 90+% of its maximum velocity in the first 22 inches. Each inch beyond that adds an incremental amount. One of the gun gurus will be able to give a definative answer on that. Feel and fit, try them both.
"I'll start spending less time with my dog and more with my wife when she starts fetching ducks for me"