I shoot 26" doubles because I do more quail hunting than pheasants and short barrels lend themselves better to the "snap" shots quail present but my next purchase may be a dedicated pheasant gun with 28" barrels.
If I was doing a lot of blocking. I would go with a nice O/U with 32" barrels.
If doing a lot of walking. It would be 28" barrels
A person has to remember, today with extended tubes. You can add near 2" to a gun just by adding extended choke tubes. It doesn't add quite the weight to the swing that true longer barrels would give but it still does add to the guns over all length.