Long barrels are not needed for load performance as 95% or more of the velocity is developed in the first 18" of the barrel for all modern loads. So adding inches after that does nothing in a practical sense to increase the performance of the load.
That said, clay target shooters tend to like longer barrels for an increased sighting plane, and moving the balance point of the gun out front a little more. The advantage being putting more weight out front which will tend to give a smoother swing and better follow through. Remember that all clay targets fly in a straight line or a smooth arc and less direction change is required of the gun barrel in tracking it.
Birds don't fly that way all the time. They can dive, dip, back-peddle, jerk, turn on a dime, and generally make your life a living Hell if you get my drift. So a more lively gun might be a better proposition, especially for upland game birds. Waterfowl - a little less so, but still capable of making a fool out of a lot of us chasers.
I just went to a Beretta A400 last year with a 26 inch barrel which is replacing my older AL 390 with a 28" tube. No regrets; and no adjustment difficulties with the shorter length. To be perfectly honest, I cannot tell the difference in the field. And the A400 does well for me at Sporting Clays also.
Remember that any pump or semi-auto with any length barrels will handle about the same as an over/under with a barrel 2 inches longer due to the receiver length in the pump/auto.
If you shoot the Tristar well, I see no need to opt in for a longer barrel gun for either upland or waterfowl.