I like a more weight-forward balance for longer, more open shots like we get on the prairie, so the 30 inch barrels seem to promote a better follow through for me. I have a CSMC Fox XE with 29 inch barrels that weighs just under 6 lbs., but has enough weight ahead of the hinge pin to keep moving. It worked very well for me on early season sharptails and huns in Montana. My DHE 20 with 30 inch barrels is my go-to open field quail gun in my Missouri home covers. For dove, I like a heavier, long barreled gun. For ducks, it doesn't matter -- I can't hit them unless they are on top of me.
In brushy cover, I find 26 inch barrels work nicely.